how to make a person

This is an exercise in making dictionaries with functions, two important objects to know in Python.

Imagine I want to make a contact list or database of people. I can use a function to represent filling out information for a person, for example

  • First Name

  • Last Name (Surname)

  • Sex

  • Year of Birth

preview

I have these tests by the end of the chapter

 1import datetime
 2import random
 3import src.person
 4import unittest
 5
 6
 7def pick_one(*choices):
 8    return random.choice(choices)
 9
10
11def get_random_name():
12    return pick_one(
13        'jane', 'joe', 'john', 'person',
14        'doe', 'smith', 'blow', 'public',
15    )
16
17
18def calculate_age(year_of_birth):
19    return (
20        datetime.datetime.now().year
21      - year_of_birth
22    )
23
24
25def get_random_year_of_birth():
26    this_year = datetime.datetime.now().year
27    return random.randint(
28        this_year-120, this_year
29    )
30
31
32class TestPerson(unittest.TestCase):
33
34    def test_factory_w_keyword_arguments(self):
35        year_of_birth = get_random_year_of_birth()
36
37        a_person = dict(
38            first_name=get_random_name(),
39            last_name=get_random_name(),
40            sex=pick_one('F', 'M'),
41        )
42
43        reality = src.person.factory(
44            **a_person,
45            year_of_birth=year_of_birth,
46        )
47        my_expectation = dict(
48            **a_person,
49            age=calculate_age(year_of_birth),
50        )
51        self.assertEqual(reality, my_expectation)
52
53    def test_factory_w_optional_arguments(self):
54        first_name = get_random_name()
55        year_of_birth = get_random_year_of_birth()
56
57        reality = src.person.factory(
58            first_name=first_name,
59            year_of_birth=year_of_birth,
60        )
61        my_expectation = dict(
62            first_name=first_name,
63            last_name='doe',
64            sex='M',
65            age=calculate_age(year_of_birth),
66        )
67        self.assertEqual(reality, my_expectation)
68
69    def test_factory_person_says_hello(self):
70        first_name = get_random_name()
71        last_name = get_random_name()
72        sex = pick_one('F', 'M')
73
74        year_of_birth = get_random_year_of_birth()
75        age = calculate_age(year_of_birth)
76
77        a_random_person = src.person.factory(
78            first_name=first_name,
79            last_name=last_name,
80            sex=sex,
81            year_of_birth=year_of_birth,
82        )
83
84        reality = src.person.say_hello(a_random_person)
85        my_expectation = (
86            f'Hi, my name is {first_name} {last_name}'
87            f' and I am {age}'
88        )
89        self.assertEqual(reality, my_expectation)
90
91
92# Exceptions seen
93# AssertionError
94# NameError
95# AttributeError
96# TypeError
97# SyntaxError

start the project

  • I name this project person

  • I open a terminal

  • I use uv to make a directory for the project and initialize it

    uv init person

    the terminal shows

    Initialized project `person` at `.../pumping_python/person`

    then goes back to the command line.

  • I change directory to the project

    cd person

    the terminal shows I am in the person folder

    .../pumping_python/person

  • I make a directory for the source code

    mkdir src

    the terminal goes back to the command line.

  • I use the mv program to change the name of main.py to person.py and move it to the src folder

    mv main.py src/person.py

    Move-Item main.py src/person.py

    the terminal goes back to the command line.

  • I make a directory for the tests

    mkdir tests

    the terminal goes back to the command line.

  • I make the tests directory a Python package

    Danger

    use 2 underscores (__) before and after init for __init__.py not _init_.py

    touch tests/__init__.py

    New-Item tests/__init__.py

    the terminal goes back to the command line.

  • I make a Python file for the tests in the tests directory

    touch tests/test_person.py

    New-Item tests/test_person.py

    the terminal goes back to the command line.

  • I open test_person.py

  • I add the first failing test to test_person.py

    1import unittest
2
3
4class TestPerson(unittest.TestCase):
5
6    def test_failure(self):
7        self.assertFalse(True)

  • I go back to the terminal to make a requirements file for the Python packages I need

    echo "pytest-watcher" > requirements.txt

    the terminal goes back to the command line.

  • I use uv to install pytest-watcher with the requirements file

    uv add --requirement requirements.txt

    the terminal shows that it installed pytest-watcher and its dependencies.

  • I add the new files and folders to git for tracking

    git add .

    the terminal goes back to the command line.

  • I add a git commit message

    git commit -am 'setup project'

    the terminal shows

    [main (root-commit) a0b12c3] setup project
 9 files changed, 148 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 .python-version
 create mode 100644 README.md
 create mode 100644 pyproject.toml
 create mode 100644 requirements.txt
 create mode 100644 src/person.py
 create mode 100644 tests/__init__.py
 create mode 100644 tests/test_person.py
 create mode 100644 uv.lock

    then goes back to the command line.

  • I use pytest-watcher to run the tests automatically

    uv run pytest-watcher . --now

    the terminal is my friend, and shows AssertionError

    ======================== FAILURES ========================
______________________ TestPerson.test_failure ________________________

self = <tests.test_person.TestPerson testMethod=test_failure>

    def test_failure(self):
>       self.assertFalse(True)
E       AssertionError: True is not false

tests/test_person.py:7: AssertionError
================ short test summary info =================
FAILED tests/test_person.py::TestPerson::test_failure - AssertionError: True is not false
=================== 1 failed in X.YZs ====================

    because True is NOT False

    if the terminal does not show the same error, then check

    • if your tests/__init__.py has two underscores (__) before and after init for __init__.py not _init_.py

    • if you ran echo "pytest-watcher" > requirements.txt, to add pytest-watcher to the requirements file

    fix those errors and try to run uv run pytest-watcher . --now again

  • I add AssertionError to the list of Exceptions seen in test_person.py

     4class TestPerson(unittest.TestCase):
 5
 6    def test_failure(self):
 7        self.assertFalse(True)
 8
 9
10# Exceptions seen
11# AssertionError

  • then I change True to False in the assertion

    7        self.assertFalse(False)

    the test passes.

test_factory_w_keyword_arguments

RED: make it fail

  • I change test_failure to test_factory_w_keyword_arguments

     4class TestPerson(unittest.TestCase):
 5
 6    def test_factory_w_keyword_arguments(self):
 7        reality = src.person.factory()
 8        my_expectation = None
 9        self.assertEqual(reality, my_expectation)
10
11
12# Exceptions seen
13# AssertionError

    the terminal is my friend, and shows NameError

    NameError: name 'src' is not defined

    because there is no definition for src in test_person.py

  • I add NameError to the list of Exceptions seen

    12# Exceptions seen
13# AssertionError
14# NameError

GREEN: make it pass

  • I add an import statement for the person module at the top of test_person.py

    1import src.person
2import unittest

  • I add AttributeError to the list of Exceptions seen

    13# Exceptions seen
14# AssertionError
15# NameError
16# AttributeError

  • I use the Explorer to open person.py from the src folder

  • I delete the text, then add a function to person.py

    1def factory():
2    return None

    the test passes.

REFACTOR: make it better

  • I want the function to take a keyword argument called first_name. I add it to the test in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10        )
11        my_expectation = None
12        self.assertEqual(reality, my_expectation)
13
14
15# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'first_name'

    because the function definition for src.person.factory does not allow calling it with inputs (the parentheses are empty) and the test sends 'first_name' as input.

  • I add TypeError to the list of Exceptions seen

    15# Exceptions seen
16# AssertionError
17# NameError
18# AttributeError
19# TypeError

  • I add first_name as an input parameter to the function in person.py

    1def factory(first_name):
2    return None

    the test passes.

  • I want the function to take a keyword argument called last_name. I add it to the test in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10            last_name='last_name',
11        )
12        my_expectation = None
13        self.assertEqual(reality, my_expectation)
14
15
16# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'last_name'.
           Did you mean 'first_name'?

    because the test called the factory function with a keyword argument (last_name) that is not in the function definition

  • I add last_name to the function definition in person.py

    1def factory(first_name, last_name):
2    return None

    the test passes.

  • I want the function to take a keyword argument called sex. I add it to the test in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10            last_name='last_name',
11            sex='M',
12        )
13        my_expectation = None
14        self.assertEqual(reality, my_expectation)
15
16
17# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'sex'

    because the test called the factory function with a keyword argument (sex) that is not in the function definition

  • I add sex as an input parameter to the factory function in person.py

    1def factory(
2        first_name, last_name,
3        sex,
4    ):
5    return None

    the test passes.

  • I want the function to take a keyword argument for year_of_birth. I add it to the test in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10            last_name='last_name',
11            sex='M',
12            year_of_birth=2000,
13        )
14        my_expectation = None
15        self.assertEqual(reality, my_expectation)
16
17
18# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'year_of_birth'

    because the test called the factory function with a keyword argument (year_of_birth) that is not in the function definition

  • I add the name to the function definition in person.py

    1def factory(
2        first_name, last_name,
3        sex, year_of_birth,
4    ):
5    return None

    the test passes.

  • I want the factory function to return a dictionary (any key-value pairs in curly braces { } separated by a comma) as output when it is called. I change my_expectation in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10            last_name='last_name',
11            sex='M',
12            year_of_birth=2000,
13        )
14        my_expectation = dict()
15        self.assertEqual(reality, my_expectation)
16
17
18# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError: None != {}

    because the function returns None and the assertion expects {}

  • I change None to a dictionary in the return statement in person.py

    1def factory(
2        first_name, last_name,
3        sex, year_of_birth,
4    ):
5    # return None
6    return {}

    the test passes because {} and dict() are two ways to make the empty dictionary.

  • I add a key called first_name to the dictionary for my_expectation, with the same value as what is given in the call to the factory function in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            first_name='first_name',
10            last_name='last_name',
11            sex='M',
12            year_of_birth=2000,
13        )
14        my_expectation = dict(
15            first_name='first_name',
16        )
17        self.assertEqual(reality, my_expectation)
18
19
20# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError: {} != {'first_name': 'first_name'}

    because the function returns the empty dictionary and the assertion expects one with first_name as the key

  • I change the return statement to give the test what it wants, in person.py

    1def factory(
2        first_name, last_name,
3        sex, year_of_birth,
4    ):
5    # return None
6    # return {}
7    return {'first_name': 'first_name'}

    the test passes.

  • I change the value of first_name to 'jane' to use a real name for reality and my_expectation, in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        reality = src.person.factory(
 9            # first_name='first_name',
10            first_name='jane',
11            last_name='last_name',
12            sex='M',
13            year_of_birth=2000,
14        )
15        my_expectation = dict(
16            # first_name='first_name',
17            first_name='jane',
18        )
19        self.assertEqual(reality, my_expectation)
20
21
22# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError: {'first_name': 'first_name'}
             != {'first_name': 'jane'}

    because I changed the value for first_name in my_expectation

  • I change the value for the first_name key in person.py

    1def factory(
2        first_name, last_name,
3        sex, year_of_birth,
4    ):
5    # return None
6    # return {}
7    # return {'first_name': 'first_name'}
8    return {'first_name': 'jane'}

    the test passes.

  • I typed the value for first_name two times in the test, which means I have to make a change in two places every time I want a different value for it. I add a variable to use to remove the repetition of 'jane' from test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9
10        reality = src.person.factory(

  • I use the variable to remove repetition of 'jane'

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9
10        reality = src.person.factory(
11            # first_name='first_name',
12            # first_name='jane',
13            first_name=first_name,
14            last_name='last_name',
15            sex='M',
16            year_of_birth=2000,
17        )
18        my_expectation = dict(
19            # first_name='first_name',
20            # first_name='jane',
21            first_name=first_name,
22        )
23        self.assertEqual(reality, my_expectation)
24
25
26# Exceptions seen

    the test is still green. I now only need to change the value of first_name in one place in the test.

  • I add a key called last_name to the dictionary, with the same value as what is given in the call to the factory function in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9
10        reality = src.person.factory(
11            # first_name='first_name',
12            # first_name='jane',
13            first_name=first_name,
14            last_name='last_name',
15            sex='M',
16            year_of_birth=2000,
17        )
18        my_expectation = dict(
19            # first_name='first_name',
20            # first_name='jane',
21            first_name=first_name,
22            last_name='last_name',
23        )
24        self.assertEqual(reality, my_expectation)
25
26
27# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane'}
 != {'first_name': 'jane', 'last_name': 'last_name'}

  • I change the return statement in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        'last_name': 'last_name',
12    }

    the test passes.

  • I change the value of last_name to 'doe' to use a real name for reality and my_expectation, in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9
10        reality = src.person.factory(
11            # first_name='first_name',
12            # first_name='jane',
13            first_name=first_name,
14            # last_name='last_name',
15            last_name='doe',
16            sex='M',
17            year_of_birth=2000,
18        )
19        my_expectation = dict(
20            # first_name='first_name',
21            # first_name='jane',
22            first_name=first_name,
23            # last_name='last_name',
24            last_name='doe',
25        )
26        self.assertEqual(reality, my_expectation)
27
28
29# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'last_name'}
 != {'first_name': 'jane', 'last_name': 'doe'}

    because I changed the value for last_name in my_expectation

  • I change the value for the last_name key in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        # 'last_name': 'last_name',
12        'last_name': 'doe',
13    }

    the test passes.

  • I typed the value for last_name two times in the test, which means I have to make a change in two places every time I want a different value for it. I add a variable to use to remove the repetition of 'doe' from test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10
11        reality = src.person.factory(

  • I use the variable to remove repetition of 'doe'

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10
11        reality = src.person.factory(
12            # first_name='first_name',
13            # first_name='jane',
14            first_name=first_name,
15            # last_name='last_name',
16            # last_name='doe',
17            last_name=last_name,
18            sex='M',
19            year_of_birth=2000,
20        )
21        my_expectation = dict(
22            # first_name='first_name',
23            # first_name='jane',
24            first_name=first_name,
25            # last_name='last_name',
26            # last_name='doe',
27            last_name=last_name,
28        )
29        self.assertEqual(reality, my_expectation)
30
31
32# Exceptions seen

    the test is still green. I now only need to change the value of first_name in one place in the test.

  • I add a key called sex to the dictionary, with the same value as what is given in the call to the factory function in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10
11        reality = src.person.factory(
12            # first_name='first_name',
13            # first_name='jane',
14            first_name=first_name,
15            # last_name='last_name',
16            # last_name='doe',
17            last_name=last_name,
18            sex='M',
19            year_of_birth=2000,
20        )
21        my_expectation = dict(
22            # first_name='first_name',
23            # first_name='jane',
24            first_name=first_name,
25            # last_name='last_name',
26            # last_name='doe',
27            last_name=last_name,
28            sex='M',
29        )
30        self.assertEqual(reality, my_expectation)
31
32
33# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError: {'first_name': 'jane', 'last_name': 'doe'}
             != {'first_name': 'jane', 'last_name': 'doe',
                 'sex': 'M'}

  • I add a new key to the return statement in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        # 'last_name': 'last_name',
12        'last_name': 'doe',
13        'sex': 'M',
14    }

    the test passes.

  • I change the value of sex to 'F' for reality and my_expectation, in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10
11        reality = src.person.factory(
12            # first_name='first_name',
13            # first_name='jane',
14            first_name=first_name,
15            # last_name='last_name',
16            # last_name='doe',
17            last_name=last_name,
18            # sex='M',
19            sex='F',
20            year_of_birth=2000,
21        )
22        my_expectation = dict(
23            # first_name='first_name',
24            # first_name='jane',
25            first_name=first_name,
26            # last_name='last_name',
27            # last_name='doe',
28            last_name=last_name,
29            # sex='M',
30            sex='F',
31        )
32        self.assertEqual(reality, my_expectation)
33
34
35# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'doe', 'sex': 'M'}
 != {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F'}

    because I changed the value for sex in my_expectation

  • I change the value for the sex key in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        # 'last_name': 'last_name',
12        'last_name': 'doe',
13        # 'sex': 'M',
14        'sex': 'F',
15    }

    the test passes.

  • I typed the value for sex two times in the test, which means I have to make a change in two places every time I want a different value for it. I add a variable to use to remove the repetition of 'F' from test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11
12        reality = src.person.factory(

  • I use the variable to remove repetition of 'F'

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11
12        reality = src.person.factory(
13            # first_name='first_name',
14            # first_name='jane',
15            first_name=first_name,
16            # last_name='last_name',
17            # last_name='doe',
18            last_name=last_name,
19            # sex='M',
20            # sex='F',
21            sex=sex,
22            year_of_birth=2000,
23        )
24        my_expectation = dict(
25            # first_name='first_name',
26            # first_name='jane',
27            first_name=first_name,
28            # last_name='last_name',
29            # last_name='doe',
30            last_name=last_name,
31            # sex='M',
32            # sex='F',
33            sex=sex,
34        )
35        self.assertEqual(reality, my_expectation)
36
37
38# Exceptions seen

    the test is still green. I now only need to change the value of sex in one place in the test.

  • I want the factory function to return the age of the person it makes. I add a key to my_expectation

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11
12        reality = src.person.factory(
13            # first_name='first_name',
14            # first_name='jane',
15            first_name=first_name,
16            # last_name='last_name',
17            # last_name='doe',
18            last_name=last_name,
19            # sex='M',
20            # sex='F',
21            sex=sex,
22            year_of_birth=2000,
23        )
24        my_expectation = dict(
25            # first_name='first_name',
26            # first_name='jane',
27            first_name=first_name,
28            # last_name='last_name',
29            # last_name='doe',
30            last_name=last_name,
31            # sex='M',
32            # sex='F',
33            sex=sex,
34            age=2026-2000,
35        )
36        self.assertEqual(reality, my_expectation)
37
38
39# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F'}
 != {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F',
     'age': 26}

  • I add a new key to the return statement in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        # 'last_name': 'last_name',
12        'last_name': 'doe',
13        # 'sex': 'M',
14        'sex': 'F',
15        'age': 26,
16    }

    the test passes.

  • I change 2000 to 1996 for reality and my_expectation, in test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11
12        reality = src.person.factory(
13            # first_name='first_name',
14            # first_name='jane',
15            first_name=first_name,
16            # last_name='last_name',
17            # last_name='doe',
18            last_name=last_name,
19            # sex='M',
20            # sex='F',
21            sex=sex,
22            # year_of_birth=2000,
23            year_of_birth=1996,
24        )
25        my_expectation = dict(
26            # first_name='first_name',
27            # first_name='jane',
28            first_name=first_name,
29            # last_name='last_name',
30            # last_name='doe',
31            last_name=last_name,
32            # sex='M',
33            # sex='F',
34            sex=sex,
35            # age=2026-2000,
36            age=2026-1996,
37        )
38        self.assertEqual(reality, my_expectation)
39
40
41# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F',
     'age': 26}
 != {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F',
     'age': 30}

    because I changed 2000 in my_expectation

  • I change the value for the age key in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    # return None
 6    # return {}
 7    # return {'first_name': 'first_name'}
 8    # return {'first_name': 'jane'}
 9    return {
10        'first_name': 'jane',
11        # 'last_name': 'last_name',
12        'last_name': 'doe',
13        # 'sex': 'M',
14        'sex': 'F',
15        # 'age': 26,
16        'age': 30,
17    }

    the test passes.

  • I remove the commented lines

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    return {
 6        'first_name': 'jane',
 7        'last_name': 'doe',
 8        'sex': 'F',
 9        'age': 30,
10    }

  • I typed the year of birth two times in the test, which means I have to make a change in two places every time I want a different value for it. I add a variable to use to remove the repetition of the year of birth from test_person.py

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11        year_of_birth = 1996
12
13        reality = src.person.factory(

  • I use the variable to remove repetition of the year of birth

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11        year_of_birth = 1996
12
13        reality = src.person.factory(
14            # first_name='first_name',
15            # first_name='jane',
16            first_name=first_name,
17            # last_name='last_name',
18            # last_name='doe',
19            last_name=last_name,
20            # sex='M',
21            # sex='F',
22            sex=sex,
23            # year_of_birth=2000,
24            # year_of_birth=1996,
25            year_of_birth=year_of_birth,
26        )
27        my_expectation = dict(
28            # first_name='first_name',
29            # first_name='jane',
30            first_name=first_name,
31            # last_name='last_name',
32            # last_name='doe',
33            last_name=last_name,
34            # sex='M',
35            # sex='F',
36            sex=sex,
37            # age=2026-2000,
38            # age=2026-1996,
39            age=2026-year_of_birth,
40        )
41        self.assertEqual(reality, my_expectation)
42
43
44# Exceptions seen

    the test is still green.

  • I remove the commented lines

     7    def test_factory_w_keyword_arguments(self):
 8        first_name = 'jane'
 9        last_name = 'doe'
10        sex = 'F'
11        year_of_birth = 1996
12
13        reality = src.person.factory(
14            first_name=first_name,
15            last_name=last_name,
16            sex=sex,
17            year_of_birth=year_of_birth,
18        )
19        my_expectation = dict(
20            first_name=first_name,
21            last_name=last_name,
22            sex=sex,
23            age=2026-year_of_birth,
24        )
25        self.assertEqual(reality, my_expectation)
26
27
28# Exceptions seen

    I now only need to change the value of sex in one place in the test.

  • I open a new terminal then change directories to person

    cd person

  • I add a git commit message in the other terminal

    git commit -am 'add test_factory_w_keyword_arguments'

    the terminal shows a summary of the changes then goes back to the command line.

test factory with random year_of_birth

There is a problem with the calculation for the age, it will be wrong if this program is run after 2026.

I want the value of the age to be a calculation based on the current year so that it will always be correct (at least most of the time).

I can do that with the datetime module from The Python Standard Library which is used for dates and times.

RED: make it fail

GREEN: make it pass

I add an import statement for the datetime module at the top of test_person.py

1import datetime
2import src.person
3import unittest

the test passes.

import datetime brings in an object (everything in Python is an object) for the datetime module so I can use it in test_person.py.

REFACTOR: make it better

I want to use random values in the test to make sure the factory function can handle different values and always calculates the right age.

  • I use a random integer (a whole number without decimals) for the year_of_birth variable

     9    def test_factory_w_keyword_arguments(self):
10        first_name = 'jane'
11        last_name = 'doe'
12        sex = 'F'
13        # year_of_birth = 1996
14        year_of_birth = random.randint(
15            datetime.datetime.now().year-120,
16            datetime.datetime.now().year
17        )
18
19        reality = src.person.factory(
20            first_name=first_name,
21            last_name=last_name,
22            sex=sex,
23            year_of_birth=year_of_birth,
24        )

    the terminal is my friend, and shows NameError

    NameError: name 'random' is not defined.
           Did you forget to import 'random'?

    • random is the random module

    • random.randint() is a call to the randint method from the random module. Okay, this one does not use the same name again

    • datetime.datetime.now().year gives me this year

    • datetime.datetime.now().year-120 gives me this year minus 120

    • random.randint(datetime.datetime.now().year-120, datetime.datetime.now().year) gives me a random number from 120 years ago, up to and including the current year

  • I add an import statement for the random module at the top of test_person.py

    1import datetime
2import random
3import src.person
4import unittest

  • I add a calculation for the age with the today method to the return statement in person.py

     1def factory(
 2        first_name, last_name,
 3        sex, year_of_birth,
 4    ):
 5    return {
 6        'first_name': 'jane',
 7        'last_name': 'doe',
 8        'sex': 'F',
 9        # 'age': 30,
10        'age': (
11            datetime.datetime.today().year
12          - year_of_birth
13        ),
14    }

    the terminal is my friend, and shows NameError

    NameError: name 'datetime' is not defined.
           Did you forget to import 'datetime'?

    because datetime is not defined in this file

  • I add an import statement for the datetime module at the top of person.py

    1import datetime
2
3
4def factory(
5        first_name, last_name,
6        sex, year_of_birth,
7    ):

    the test passes.

    import datetime brings in an object (everything in Python is an object) for the datetime module so I can use it in person.py.

  • I add a variable

     9    def test_factory_w_keyword_arguments(self):
10        first_name = 'jane'
11        last_name = 'doe'
12        sex = 'F'
13        # year_of_birth = 1996
14        this_year = datetime.datetime.now().year
15        year_of_birth = random.randint(
16            datetime.datetime.now().year-120,
17            datetime.datetime.now().year
18        )

  • I use the variable to remove repetition of datetime.datetime.now().year from the test

     9    def test_factory_w_keyword_arguments(self):
10        first_name = 'jane'
11        last_name = 'doe'
12        sex = 'F'
13        # year_of_birth = 1996
14        this_year = datetime.datetime.now().year
15        year_of_birth = random.randint(
16            # datetime.datetime.now().year-120,
17            # datetime.datetime.now().year
18            this_year-120, this_year
19        )
20
21        reality = src.person.factory(
22            first_name=first_name,
23            last_name=last_name,
24            sex=sex,
25            year_of_birth=year_of_birth,
26        )
27        my_expectation = dict(
28            first_name=first_name,
29            last_name=last_name,
30            sex=sex,
31            # age=2026-year_of_birth,
32            # age=(
33            #     datetime.datetime.today().year
34            #   - year_of_birth
35            # ),
36            age=this_year-year_of_birth,
37        )
38        self.assertEqual(reality, my_expectation)
39
40
41# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am 'use random values for age'

    the terminal shows a summary of the changes then goes back to the command line.

test factory with random sex

RED: make it fail

  • I go back to the terminal that is running the tests

  • I add randomness to the sex variable in test_person.py

     9    def test_factory_w_keyword_arguments(self):
10        first_name = 'jane'
11        last_name = 'doe'
12        # sex = 'F'
13        sex = random.choice(('F', 'M'))
14        # year_of_birth = 1996
15        this_year = datetime.datetime.now().year
16        year_of_birth = random.randint(
17            # datetime.datetime.now().year-120,
18            # datetime.datetime.now().year
19            this_year-120, this_year
20        )

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes if sex is randomly 'F'.

    If sex is randomly 'M', the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'doe', 'sex': 'F',
     'age': X}
 != {'first_name': 'jane', 'last_name': 'doe', 'sex': 'M',
     'age': X}

    where X is the random age

GREEN: make it pass

  • I add the sex input parameter instead of a value that does not change, to the return statement in person.py

     4def factory(
 5        first_name, last_name,
 6        sex, year_of_birth,
 7    ):
 8    return {
 9        'first_name': 'jane',
10        'last_name': 'doe',
11        # 'sex': 'F',
12        'sex': sex,
13        # 'age': 30,
14        'age': (
15            datetime.datetime.today().year
16          - year_of_birth
17        ),
18    }

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes with no more random failures

  • I add a git commit message in the other terminal

    git commit -am 'use random values for sex'

    the terminal shows a summary of the changes then goes back to the command line.

test factory with random last name

RED: make it fail

  • I go back to the terminal that is running the tests

  • I use random.choice for the last_name variable in test_person.py

     9    def test_factory_w_keyword_arguments(self):
10        first_name = 'jane'
11        # last_name = 'doe'
12        last_name = random.choice((
13            'doe', 'smith', 'blow', 'public',
14        ))
15        # sex = 'F'
16        sex = random.choice(('F', 'M'))
17        # year_of_birth = 1996
18        this_year = datetime.datetime.now().year
19        year_of_birth = random.randint(
20            # datetime.datetime.now().year-120,
21            # datetime.datetime.now().year
22            this_year-120, this_year
23        )

  • I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes if last_name is 'doe'.

    If last_name is NOT doe, the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': 'doe', 'sex': Y,
     'age': X}
 != {'first_name': 'jane', 'last_name': Z,     'sex': Y,
     'age': X}

    where Z is the random last name, X is the random age, and Y is the random sex.

GREEN: make it pass

  • I use the last_name input parameter as the value for the 'last_name' key in the return statement in person.py

     4def factory(
 5        first_name, last_name,
 6        sex, year_of_birth,
 7    ):
 8    return {
 9        'first_name': 'jane',
10        # 'last_name': 'doe',
11        'last_name': last_name,
12        # 'sex': 'F',
13        'sex': sex,
14        # 'age': 30,
15        'age': (
16            datetime.datetime.today().year
17          - year_of_birth
18        ),
19    }

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes with no more random failures

  • I add a git commit message in the other terminal

    git commit -am 'use random values for last_name'

    the terminal shows a summary of the changes then goes back to the command line.

test factory with random first name

RED: make it fail

  • I go back to the terminal that is running the tests

  • I add randomness to the first_name variable in test_person.py

     9    def test_factory_w_keyword_arguments(self):
10        # first_name = 'jane'
11        first_name = random.choice((
12            'jane', 'joe', 'john', 'person',
13        ))
14        # last_name = 'doe'
15        last_name = random.choice((
16            'doe', 'smith', 'blow', 'public',
17        ))
18        # sex = 'F'
19        sex = random.choice(('F', 'M'))
20        # year_of_birth = 1996
21        this_year = datetime.datetime.now().year
22        year_of_birth = random.randint(
23            # datetime.datetime.now().year-120,
24            # datetime.datetime.now().year
25            this_year-120, this_year
26        )

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes if first_name is 'jane'.

    If first_name is not 'jane' the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': 'jane', 'last_name': Z, 'sex': Y, 'age': X}
 != {'first_name': A,      'last_name': Z, 'sex': Y, 'age': X}

    where A is the random first name, X is the random age, Y is the random sex, and Z is the random last name

GREEN: make it pass

I add the first_name input parameter instead of a value that does not change, to the return statement in person.py

 4def factory(
 5        first_name, last_name,
 6        sex, year_of_birth,
 7    ):
 8    return {
 9        # 'first_name': 'jane',
10        'first_name': first_name,
11        # 'last_name': 'doe',
12        'last_name': last_name,
13        # 'sex': 'F',
14        'sex': sex,
15        # 'age': 30,
16        'age': (
17            datetime.datetime.today().year
18          - year_of_birth
19        ),
20    }

I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes with no more random failures

REFACTOR: make it better

  • I remove the commented lines

     4def factory(
 5        first_name, last_name,
 6        sex, year_of_birth,
 7    ):
 8    return {
 9        'first_name': first_name,
10        'last_name': last_name,
11        'sex': sex,
12        'age': (
13            datetime.datetime.today().year
14          - year_of_birth
15        ),
16    }

  • I add a git commit message in the other terminal

    git commit -am 'use random values for first_name'

    the terminal shows a summary of the changes then goes back to the command line.

extract pick_one function

  • I go back to the terminal that is running the tests

  • I add a function for the calls to the random.choice method

     1import datetime
 2import random
 3import src.person
 4import unittest
 5
 6
 7def pick_one(choices):
 8    return random.choice(choices)
 9
10
11class TestPerson(unittest.TestCase):
12
13    def test_factory_w_keyword_arguments(self):

  • I use the new function to remove repetition of random.choice from the test

    13    def test_factory_w_keyword_arguments(self):
14        # first_name = 'jane'
15        # first_name = random.choice((
16        #     'jane', 'joe', 'john', 'person',
17        # ))
18        first_name = pick_one(
19            'jane', 'joe', 'john', 'person',
20        )
21        # last_name = 'doe'
22        # last_name = random.choice((
23        #     'doe', 'smith', 'blow', 'public',
24        # ))
25        last_name = pick_one(
26            'doe', 'smith', 'blow', 'public',
27        )
28        # sex = 'F'
29        # sex = random.choice(('F', 'M'))
30        sex = pick_one('F', 'M')
31        # year_of_birth = 1996
32        this_year = datetime.datetime.now().year
33        year_of_birth = random.randint(
34            # datetime.datetime.now().year-120,
35            # datetime.datetime.now().year
36            this_year-120, this_year
37        )

    the terminal is my friend, and shows TypeError

    TypeError: pick_one() takes 1 positional argument
           but 4 were given

    because the function definition only takes one input and the test sends four for first_name, four for last_name and two for sex.

    I want the function to be able to take any number of arguments I send, without it knowing how many I will send.

  • I change the definition of the pick_one function with a starred expression like I did in test_w_unknown_arguments so that it can take any number of positional arguments

    7def pick_one(*choices):
8    return random.choice(choices)

    the test is green again, because Python reads the positional arguments as a tuple in the function since I used a starred expression (*choices)

  • I add a git commit message in the other terminal

    git commit -am 'extract pick_one function'

    the terminal shows a summary of the changes then goes back to the command line.

test factory with a dictionary

The difference between the call to the factory function and the expected dictionary in the test is that one has a year of birth and the other does a calculation with the year of birth. The other things are the same.

RED: make it fail

  • I go back to the terminal that is running the tests

  • I add a dictionary to use to remove the repeating parts

    13    def test_factory_w_keyword_arguments(self):
14        # first_name = 'jane'
15        # first_name = random.choice((
16        #     'jane', 'joe', 'john', 'person',
17        # ))
18        first_name = pick_one(
19            'jane', 'joe', 'john', 'person',
20        )
21        # last_name = 'doe'
22        # last_name = random.choice((
23        #     'doe', 'smith', 'blow', 'public',
24        # ))
25        last_name = pick_one(
26            'doe', 'smith', 'blow', 'public',
27        )
28        # sex = 'F'
29        # sex = random.choice(('F', 'M'))
30        sex = pick_one('F', 'M')
31        # year_of_birth = 1996
32        this_year = datetime.datetime.now().year
33        year_of_birth = random.randint(
34            # datetime.datetime.now().year-120,
35            # datetime.datetime.now().year
36            this_year-120, this_year
37        )
38
39        a_person = dict(
40            first_name=first_name,
41            last_name=last_name,
42            sex=sex,
43        )
44
45        reality = src.person.factory(
46            first_name=first_name,
47            last_name=last_name,
48            sex=sex,
49            year_of_birth=year_of_birth,
50        )
51        my_expectation = dict(
52            first_name=first_name,
53            last_name=last_name,
54            sex=sex,
55            # age=2026-year_of_birth,
56            # age=(
57            #     datetime.datetime.today().year
58            #   - year_of_birth
59            # ),
60            age=this_year-year_of_birth,
61        )
62        self.assertEqual(reality, my_expectation)
63
64
65# Exceptions seen

  • I use the new variable to remove the repeating parts

    39        a_person = dict(
40            first_name=first_name,
41            last_name=last_name,
42            sex=sex,
43        )
44
45        reality = src.person.factory(
46            # first_name=first_name,
47            # last_name=last_name,
48            # sex=sex,
49            a_person,
50            year_of_birth=year_of_birth,
51        )
52        my_expectation = dict(
53            # first_name=first_name,
54            # last_name=last_name,
55            # sex=sex,
56            a_person,
57            # age=2026-year_of_birth,
58            # age=(
59            #     datetime.datetime.today().year
60            #   - year_of_birth
61            # ),
62            age=this_year-year_of_birth,
63        )
64        self.assertEqual(reality, my_expectation)
65
66
67# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: factory() missing 2 required
           positional arguments: 'last_name' and 'sex'

    because the factory function now takes a_person as the first positional argument (first_name), and wants the other required arguments.

    I want the function to take the key-value pairs of the dictionary (a_person) as keyword arguments.

GREEN: make it pass

I use a double starred expression for the dictionary like I did in test_w_unknown_arguments

45        reality = src.person.factory(
46            # first_name=first_name,
47            # last_name=last_name,
48            # sex=sex,
49            **a_person,
50            year_of_birth=year_of_birth,
51        )
52        my_expectation = dict(
53            # first_name=first_name,
54            # last_name=last_name,
55            # sex=sex,
56            **a_person,
57            # age=2026-year_of_birth,
58            # age=(
59            #     datetime.datetime.today().year
60            #   - year_of_birth
61            # ),
62            age=this_year-year_of_birth,
63        )
64        self.assertEqual(reality, my_expectation)
65
66
67# Exceptions seen

the test is green again, because Python sends the dictionary as keyword arguments since I used a double starred expression (*choices).

REFACTOR: make it better

  • I use the values of first_name, last_name and the sex variables in the a_person dictionary because they are now only used once, by a_person

    13    def test_factory_w_keyword_arguments(self):
14        # first_name = 'jane'
15        # first_name = random.choice((
16        #     'jane', 'joe', 'john', 'person',
17        # ))
18        # first_name = pick_one(
19        #     'jane', 'joe', 'john', 'person',
20        # )
21        # last_name = 'doe'
22        # last_name = random.choice((
23        #     'doe', 'smith', 'blow', 'public',
24        # ))
25        # last_name = pick_one(
26        #     'doe', 'smith', 'blow', 'public',
27        # )
28        # sex = 'F'
29        # sex = random.choice(('F', 'M'))
30        # sex = pick_one('F', 'M')
31        # year_of_birth = 1996
32        this_year = datetime.datetime.now().year
33        year_of_birth = random.randint(
34            # datetime.datetime.now().year-120,
35            # datetime.datetime.now().year
36            this_year-120, this_year
37        )
38
39        a_person = dict(
40            # first_name=first_name,
41            # last_name=last_name,
42            # sex=sex,
43            first_name=pick_one(
44                'jane', 'joe', 'john', 'person',
45            ),
46            last_name=pick_one(
47                'doe', 'smith', 'blow', 'public',
48            ),
49            sex=pick_one('F', 'M'),
50        )

    still green.

  • I make a function with a tuple of all the names for the test to have more random names to pick from

     7def pick_one(*choices):
 8    return random.choice(choices)
 9
10
11def get_random_name():
12    return pick_one(
13        'jane', 'joe', 'john', 'person',
14        'doe', 'smith', 'blow', 'public',
15    )
16
17
18class TestPerson(unittest.TestCase):
19
20    def test_factory_w_keyword_arguments(self):

  • I use the function in the a_person dictionary

    46        a_person = dict(
47            # first_name=first_name,
48            # last_name=last_name,
49            # sex=sex,
50            # first_name=pick_one(
51            #     'jane', 'joe', 'john', 'person',
52            # ),
53            # last_name=pick_one(
54            #     'doe', 'smith', 'blow', 'public',
55            # ),
56            first_name=get_random_name(),
57            last_name=get_random_name(),
58            sex=pick_one('F', 'M'),
59        )

    green.

  • I remove the commented lines

    20    def test_factory_w_keyword_arguments(self):
21        this_year = datetime.datetime.now().year
22        year_of_birth = random.randint(
23            this_year-120, this_year
24        )
25
26        a_person = dict(
27            first_name=get_random_name(),
28            last_name=get_random_name(),
29            sex=pick_one('F', 'M'),
30        )
31
32        reality = src.person.factory(
33            **a_person,
34            year_of_birth=year_of_birth,
35        )
36        my_expectation = dict(
37            **a_person,
38            age=this_year-year_of_birth,
39        )
40        self.assertEqual(reality, my_expectation)
41
42
43# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am 'extract a_person dictionary'

    the terminal shows a summary of the changes then goes back to the command line.

test_factory_w_optional_arguments

I want to see what happens when I try to make a person without a value for the last_name argument.

RED: make it fail

  • I go back to the terminal that is running the tests

  • I make a copy of test_factory_w_keyword_arguments and paste it below in test_person.py

    32        reality = src.person.factory(
33            **a_person,
34            year_of_birth=year_of_birth,
35        )
36        my_expectation = dict(
37            **a_person,
38            age=this_year-year_of_birth,
39        )
40        self.assertEqual(reality, my_expectation)
41
42    def test_factory_w_keyword_arguments(self):
43        a_person = dict(
44            first_name=get_random_name(),
45            last_name=get_random_name(),
46            sex=pick_one('F', 'M'),
47        )
48
49        this_year = datetime.datetime.now().year
50        year_of_birth = random.randint(
51            this_year-120, this_year
52        )
53
54        reality = src.person.factory(
55            **a_person,
56            year_of_birth=year_of_birth,
57        )
58        my_expectation = dict(
59            **a_person,
60            age=this_year-year_of_birth,
61        )
62        self.assertEqual(reality, my_expectation)
63
64
65# Exceptions seen

  • I change the name of the new test to test_factory_w_optional_arguments

    32        reality = src.person.factory(
33            **a_person,
34            year_of_birth=year_of_birth,
35        )
36        my_expectation = dict(
37            **a_person,
38            age=this_year-year_of_birth,
39        )
40        self.assertEqual(reality, my_expectation)
41
42    def test_factory_w_optional_arguments(self):
43        a_person = dict(
44            first_name=get_random_name(),
45            last_name=get_random_name(),
46            sex=pick_one('F', 'M'),
47        )

  • I comment out the last_name key-value pair in the a_person dictionary

    42    def test_factory_w_optional_arguments(self):
43        this_year = datetime.datetime.now().year
44        year_of_birth = random.randint(
45            this_year-120, this_year
46        )
47
48        a_person = dict(
49            first_name=get_random_name(),
50            # last_name=get_random_name(),
51            sex=pick_one('F', 'M'),
52        )

    the terminal is my friend, and shows TypeError

    TypeError: factory() missing 1 required
           positional argument: 'last_name'

    because this test no longer gives a value for last_name when it calls the factory function, I have to make it a choice.

GREEN: make it pass

REFACTOR: make it better

  • I comment out the sex key in test_factory_w_optional_arguments to see what happens when I call the factory function without it, in test_person.py

    42    def test_factory_w_optional_arguments(self):
43        this_year = datetime.datetime.now().year
44        year_of_birth = random.randint(
45            this_year-120, this_year
46        )
47
48        a_person = dict(
49            first_name=get_random_name(),
50            # last_name=get_random_name(),
51            # sex=pick_one('F', 'M'),
52        )

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': Z, 'last_name': Y,
     'sex': None, 'age': X}
 != {'first_name': Z, 'last_name': Y, 'age': X}

    the factory function returns a dictionary with a 'sex' key, and the assertion expects a dictionary without that key

  • I add a key-value pair for sex to my_expectation in test_factory_w_optional_arguments

    54        reality = src.person.factory(
55            **a_person,
56            year_of_birth=year_of_birth,
57        )
58        my_expectation = dict(
59            **a_person,
60            last_name='doe',
61            sex='M',
62            age=this_year-year_of_birth,
63        )
64        self.assertEqual(reality, my_expectation)
65
66
67# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': Y, 'last_name': 'doe',
     'sex': None, 'age': X}
 != {'first_name': Y, 'last_name': 'doe',
     'sex': 'M', 'age': X}

    because the factory function returns a dictionary with a value of None for sex and the assertion expects 'M'

  • I change the default value for sex in the factory function in person.py

     4def factory(
 5        first_name, last_name='doe',
 6        sex='M', year_of_birth=None,
 7    ):
 8    return {
 9        'first_name': first_name,
10        'last_name': last_name,
11        'sex': sex,
12        'age': datetime.datetime.now().year-year_of_birth,
13    }

    the test passes because the default value for the sex parameter of the function is 'M'. This means that

    src.person.factory(
    first_name=first_name,
    year_of_birth=year_of_birth,
)

    is the same as

    src.person.factory(
    first_name=first_name,
    year_of_birth=year_of_birth,
    last_name='doe',
    sex='M',
)

    because a function uses the default value for a parameter when it is called without the parameter.

  • I no longer need the a_person dictionary in test_factory_w_optional_arguments because it only has one key, I can use a variable for first_name instead

    42    def test_factory_w_optional_arguments(self):
43        first_name = get_random_name()
44        this_year = datetime.datetime.now().year
45        year_of_birth = random.randint(
46            this_year-120, this_year
47        )

  • I use the variable for reality and my_expectation

    55        reality = src.person.factory(
56            **a_person,
57            first_name=first_name,
58            year_of_birth=year_of_birth,
59        )
60        my_expectation = dict(
61            **a_person,
62            first_name=first_name,
63            last_name='doe',
64            sex='M',
65            age=this_year-year_of_birth,
66        )
67        self.assertEqual(reality, my_expectation)
68
69
70# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: src.person.factory() got multiple values
           for keyword argument 'first_name'

    because the a_person dictionary has a key called first_name, the call to src.person.factory gets called with the same keyword argument twice.

  • I comment out **a_person,

    Tip

    I can comment out a line in Visual Studio Code with ctrl/command+/ anywhere on the line

    55        reality = src.person.factory(
56            # **a_person,
57            first_name=first_name,
58            year_of_birth=year_of_birth,
59        )
60        my_expectation = dict(
61            # **a_person,
62            first_name=first_name,
63            last_name='doe',
64            sex='M',
65            age=this_year-year_of_birth,
66        )
67        self.assertEqual(reality, my_expectation)
68
69
70# Exceptions seen

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes with no more random failures

  • I remove the commented lines and the a_person dictionary

    42    def test_factory_w_optional_arguments(self):
43        first_name = get_random_name()
44        this_year = datetime.datetime.now().year
45        year_of_birth = random.randint(
46            this_year-120, this_year
47        )
48
49        reality = src.person.factory(
50            first_name=first_name,
51            year_of_birth=year_of_birth,
52        )
53        my_expectation = dict(
54            first_name=first_name,
55            last_name='doe',
56            sex='M',
57            age=this_year-year_of_birth,
58        )
59        self.assertEqual(reality, my_expectation)
60
61
62# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am \
'add test_factory_w_optional_arguments'

    the terminal shows a summary of the changes then goes back to the command line.

test_factory_person_says_hello

I have a function that takes in first_name, last_name, sex and year_of_birth for a person and returns a dictionary with first_name, last_name, sex and age (based on the year_of_birth) as keys.

What if I want the person to say hello, How would I do that? I can write a function that takes in a person (dictionary) and returns a message (string).

RED: make it fail

  • I add a new test to test_person.py

    49        reality = src.person.factory(
50            first_name=first_name,
51            year_of_birth=year_of_birth,
52        )
53        my_expectation = dict(
54            first_name=first_name,
55            last_name='doe',
56            sex='M',
57            age=this_year-year_of_birth,
58        )
59        self.assertEqual(reality, my_expectation)
60
61    def test_factory_person_says_hello(self):
62        joe = src.person.factory(
63            first_name='joe',
64            last_name='blow',
65            year_of_birth=1996,
66        )
67
68        reality = src.person.say_hello(joe)
69        my_expectation = None
70        self.assertEqual(reality, my_expectation)
71
72
73# Exceptions seen

    the terminal is my friend, and shows AttributeError

    AttributeError: module 'src.person'
                has no attribute 'hello'

    because person.py does not have a function named say_hello, yet.

GREEN: make it pass

  • I add the function to person.py

     4def factory(
 5        first_name, last_name='doe',
 6        sex='M', year_of_birth=None,
 7    ):
 8    return {
 9        'first_name': first_name,
10        'last_name': last_name,
11        'sex': sex,
12        'age': (
13            datetime.datetime.today().year
14          - year_of_birth
15        ),
16    }
17
18
19def say_hello():
20    return None

    the terminal is my friend, and shows TypeError

    TypeError: hello() takes
           0 positional arguments but 1 was given

    because the definition for say_hello does not allow inputs and the test called the function with a positional argument (person)

  • I add a name to the definition

    19def say_hello(person):
20    return None

    the test passes.

REFACTOR: make it better

I want the say_hello function to return a string for the person (dictionary) I give as input

  • I change my_expectation to an f-string in test_factory_person_says_hello in test_person.py

    62    def test_factory_person_says_hello(self):
63        joe = src.person.factory(
64            first_name='joe',
65            last_name='blow',
66            year_of_birth=1996,
67        )
68
69        reality = src.person.say_hello(joe)
70        # my_expectation = None
71        my_expectation = (
72            'Hi, my name is joe blow and I am'
73            f' {datetime.datetime.now().year-1996}'
74        )
75        self.assertEqual(reality, my_expectation)
76
77
78# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    None != 'Hi, my name is joe blow and I am 30'

  • I copy (ctrl/command+c) the value from the terminal and paste it (ctrl/command+v) in the return statement in person.py

    19def say_hello(person):
20    # return None
21    return 'Hi, my name is joe blow and I am 30'

    the test passes.

  • I add an assertion for another person to test_factory_person_says_hello in test_person.py

    68        reality = src.person.say_hello(joe)
69        # my_expectation = None
70        my_expectation = (
71            'Hi, my name is joe blow and I am'
72            f' {datetime.datetime.now().year-1996}'
73        )
74        self.assertEqual(reality, my_expectation)
75
76        jane = src.person.factory(
77            first_name='jane',
78            sex='F',
79            year_of_birth=1991,
80        )
81
82        reality = src.person.say_hello(jane)
83        my_expectation = (
84            'Hi, my name is jane doe and I am'
85            f' {datetime.datetime.now().year-1991}'
86        )
87        self.assertEqual(reality, my_expectation)
88
89
90# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
      'Hi, my name is joe blow and I am 30'
   != 'Hi, my name is jane doe and I am 35'

    I have to make sure the say_hello function uses the values of the person dictionary to make the message. I can do that with the get method of dictionaries.

  • I change the string to an f-string with the value for the first_name in person.py

    19def say_hello(person):
20    first_name = person.get('first_name')
21
22    # return None
23    # return 'Hi, my name is joe blow and I am 30'
24    return (
25        f'Hi, my name is {first_name}'
26        ' blow and I am 30'
27    )

    the terminal is my friend, and shows AssertionError

    AssertionError:
    'Hi, my name is jane blow and I am 30'
 != 'Hi, my name is jane doe and I am 35'

    • the first names are the same because person.get('first_name') uses the get method of the dictionary to get the value of the 'first_name' key

    • the last names and ages are different

  • I use the get method of the dictionary to get the value for the last_name key, then add it to the return statement

    19def say_hello(person):
20    first_name = person.get('first_name')
21    last_name = person.get('last_name')
22
23    # return None
24    # return 'Hi, my name is joe blow and I am 30'
25    return (
26        # f'Hi, my name is {first_name}'
27        # ' blow and I am 30'
28        f'Hi, my name is {first_name} {last_name}'
29        ' and I am 30'
30    )

    the terminal is my friend, and shows AssertionError

    AssertionError:
    'Hi, my name is jane doe and I am 30'
 != 'Hi, my name is jane doe and I am 35'

    the age is the only thing that is different

  • I use the get method of the dictionary to get the value for the age key , then add it to the return statement

    19def say_hello(person):
20    first_name = person.get('first_name')
21    last_name = person.get('last_name')
22    age = person.get('age')
23
24    # return None
25    # return 'Hi, my name is joe blow and I am 30'
26    return (
27        # f'Hi, my name is {first_name}'
28        # ' blow and I am 30'
29        f'Hi, my name is {first_name} {last_name}'
30        # ' and I am 30'
31        f' and I am {age}'
32    )

    the test passes.

  • I remove the commented lines

    19def say_hello(person):
20    first_name = person.get('first_name')
21    last_name = person.get('last_name')
22    age = person.get('age')
23
24    return (
25        f'Hi, my name is {first_name} {last_name}'
26        f' and I am {age}'
27    )

  • I add an assertion for a new person to test_factory_person_says_hello in test_person.py

     76        jane = src.person.factory(
 77            first_name='jane',
 78            sex='F',
 79            year_of_birth=1991,
 80        )
 81
 82        reality = src.person.say_hello(jane)
 83        my_expectation = (
 84            'Hi, my name is jane doe and I am'
 85            f' {datetime.datetime.now().year-1991}'
 86        )
 87        self.assertEqual(reality, my_expectation)
 88
 89        john = src.person.factory(
 90            first_name='john',
 91            last_name='smith',
 92            year_of_birth=1580,
 93        )
 94
 95        reality = src.person.say_hello(john)
 96        my_expectation = (
 97            'Hi, my name is jane doe and I am'
 98            f' {datetime.datetime.now().year-1991}'
 99        )
100        self.assertEqual(reality, my_expectation)
101
102
103# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    'Hi, my name is john smith and I am 446'
 != 'Hi, my name is jane doe and I am 35'

  • I change my_expectation to match reality for john

     89        john = src.person.factory(
 90            first_name='john',
 91            last_name='smith',
 92            year_of_birth=1580,
 93        )
 94
 95        reality = src.person.say_hello(john)
 96        my_expectation = (
 97            # 'Hi, my name is jane doe and I am'
 98            # f' {datetime.datetime.now().year-1991}'
 99            'Hi, my name is john smith and I am'
100            f' {datetime.datetime.now().year-1580}'
101        )
102        self.assertEqual(reality, my_expectation)
103
104
105# Exceptions seen

    the test passes.

  • I add an assertion for one more person

     95        reality = src.person.say_hello(john)
 96        my_expectation = (
 97            # 'Hi, my name is jane doe and I am'
 98            # f' {datetime.datetime.now().year-1991}'
 99            'Hi, my name is john smith and I am'
100            f' {datetime.datetime.now().year-1580}'
101        )
102        self.assertEqual(reality, my_expectation)
103
104        a_person = src.person.factory(
105            first_name='person',
106            last_name='public',
107            year_of_birth=2000,
108            sex='F',
109        )
110
111        reality = src.person.say_hello(a_person)
112        my_expectation = (
113            'Hi, my name is john smith and I am'
114            f' {datetime.datetime.now().year-1580}'
115        )
116        self.assertEqual(reality, my_expectation)
117
118
119# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError:
    'Hi, my name is person public and I am 26'
 != 'Hi, my name is john smith and I am 446'

  • I change my_expectation to match reality for a_person

    104        a_person = src.person.factory(
105            first_name='person',
106            last_name='public',
107            year_of_birth=2000,
108            sex='F',
109        )
110
111        reality = src.person.say_hello(a_person)
112        my_expectation = (
113            # 'Hi, my name is john smith and I am'
114            # f' {datetime.datetime.now().year-1580}'
115            'Hi, my name is person public and I am'
116            f' {datetime.datetime.now().year-2000}'
117        )
118        self.assertEqual(reality, my_expectation)
119
120
121# Exceptions seen

    the test passes.

  • I add variables to use them to remove repetition of 'person', 'public', 2000 and the age calculation from the last assertion

     95        reality = src.person.say_hello(john)
 96        my_expectation = (
 97            # 'Hi, my name is jane doe and I am'
 98            # f' {datetime.datetime.now().year-1991}'
 99            'Hi, my name is john smith and I am'
100            f' {datetime.datetime.now().year-1580}'
101        )
102        self.assertEqual(reality, my_expectation)
103
104        first_name = 'person'
105        last_name = 'public'
106        year_of_birth = 2000
107        age = (
108            datetime.datetime.now().year
109          - year_of_birth
110        )
111
112        a_person = src.person.factory(
113            first_name='person',
114            last_name='public',
115            year_of_birth=2000,
116            sex='F',
117        )

  • I use the variables to remove repetition of 'person', 'public', 2000 and the age calculation

    104        first_name = 'person'
105        last_name = 'public'
106        year_of_birth = 2000
107        age = (
108            datetime.datetime.now().year
109          - year_of_birth
110        )
111
112        a_person = src.person.factory(
113            # first_name='person',
114            # last_name='public',
115            # year_of_birth=2000,
116            first_name=first_name,
117            last_name=last_name,
118            year_of_birth=year_of_birth,
119            sex='F',
120        )
121
122        reality = src.person.say_hello(a_person)
123        my_expectation = (
124            # 'Hi, my name is john smith and I am'
125            # f' {datetime.datetime.now().year-1580}'
126            # 'Hi, my name is person public and I am'
127            # f' {datetime.datetime.now().year-2000}'
128            f'Hi, my name is {first_name} {last_name}'
129            f' and I am {age}'
130        )
131        self.assertEqual(reality, my_expectation)
132
133
134# Exceptions seen

    the test is still green.

  • I add variables to use them to remove repetition of 'john', 'smith', 1580 and the age calculation from the assertion before the one for a_person

     82        reality = src.person.say_hello(jane)
 83        my_expectation = (
 84            'Hi, my name is jane doe and I am'
 85            f' {datetime.datetime.now().year-1991}'
 86        )
 87        self.assertEqual(reality, my_expectation)
 88
 89        first_name = 'john'
 90        last_name = 'smith'
 91        year_of_birth = 1580
 92        age = (
 93            datetime.datetime.now().year
 94          - year_of_birth
 95        )
 96
 97        john = src.person.factory(
 98            first_name='john',
 99            last_name='smith',
100            year_of_birth=1580,
101        )

  • I use the variables to remove repetition of 'john', 'smith', 1580 and the age calculation

    68        reality = src.person.say_hello(joe)
69        # my_expectation = None
70        my_expectation = (
71            'Hi, my name is joe blow and I am'
72            f' {datetime.datetime.now().year-1996}'
73        )
74        self.assertEqual(reality, my_expectation)
75
76        first_name = 'jane'
77        last_name = 'doe'
78        year_of_birth = 1991
79        age = (
80            datetime.datetime.now().year
81          - year_of_birth
82        )
83
84        jane = src.person.factory(
85            first_name='jane',
86            sex='F',
87            year_of_birth=1991,
88        )

    still green.

  • I add the same variable names to use them to remove repetition of 'jane', 1991 and the age calculation from the second assertion

    68        reality = src.person.say_hello(joe)
69        # my_expectation = None
70        my_expectation = (
71            'Hi, my name is joe blow and I am'
72            f' {datetime.datetime.now().year-1996}'
73        )
74        self.assertEqual(reality, my_expectation)
75
76        first_name = 'jane'
77        last_name = 'doe'
78        year_of_birth = 1991
79        age = (
80            datetime.datetime.now().year
81          - year_of_birth
82        )
83
84        jane = src.person.factory(
85            first_name='jane',
86            sex='F',
87            year_of_birth=1991,
88        )

  • I use the variables to remove repetition of 'jane', 1991 and the age calculation

     76        first_name = 'jane'
 77        last_name = 'doe'
 78        year_of_birth = 1991
 79        age = (
 80            datetime.datetime.now().year
 81          - year_of_birth
 82        )
 83
 84        jane = src.person.factory(
 85            # first_name='jane',
 86            sex='F',
 87            # year_of_birth=1991,
 88            first_name=first_name,
 89            year_of_birth=year_of_birth,
 90        )
 91
 92        reality = src.person.say_hello(jane)
 93        my_expectation = (
 94            # 'Hi, my name is jane doe and I am'
 95            # f' {datetime.datetime.now().year-1991}'
 96            f'Hi, my name is {first_name} {last_name}'
 97            f' and I am {age}'
 98        )
 99        self.assertEqual(reality, my_expectation)
100
101        first_name = 'john'
102        last_name = 'smith'
103        year_of_birth = 1580
104        age = (
105            datetime.datetime.now().year
106          - year_of_birth
107        )

    green.

  • I add the variable names to use them to remove repetition of 'joe', 'blow', 1996 and the age calculation from the first assertion

    61    def test_factory_person_says_hello(self):
62        first_name = 'joe'
63        last_name = 'blow'
64        year_of_birth = 1996
65        age = (
66            datetime.datetime.now().year
67          - year_of_birth
68        )
69
70        joe = src.person.factory(
71            first_name='joe',
72            last_name='blow',
73            year_of_birth=1996,
74        )

  • I use the variables to remove repetition of 'joe', 'blow', 1996 and the age calculation

    61    def test_factory_person_says_hello(self):
62        first_name = 'joe'
63        last_name = 'blow'
64        year_of_birth = 1996
65        age = (
66            datetime.datetime.now().year
67          - year_of_birth
68        )
69
70        joe = src.person.factory(
71            # first_name='joe',
72            # last_name='blow',
73            # year_of_birth=1996,
74            first_name=first_name,
75            last_name=last_name,
76            year_of_birth=year_of_birth,
77        )
78
79        reality = src.person.say_hello(joe)
80        # my_expectation = None
81        my_expectation = (
82            # 'Hi, my name is joe blow and I am'
83            # f' {datetime.datetime.now().year-1996}'
84            f'Hi, my name is {first_name} {last_name}'
85            f' and I am {age}'
86        )
87        self.assertEqual(reality, my_expectation)
88
89        first_name = 'jane'
90        last_name = 'doe'
91        year_of_birth = 1991
92        age = (
93            datetime.datetime.now().year
94          - year_of_birth
95        )

    the test is still green.

  • I remove the commented lines

     61    def test_factory_person_says_hello(self):
 62        first_name = 'joe'
 63        last_name = 'blow'
 64        year_of_birth = 1996
 65        age = (
 66            datetime.datetime.now().year
 67          - year_of_birth
 68        )
 69
 70        joe = src.person.factory(
 71            first_name=first_name,
 72            last_name=last_name,
 73            year_of_birth=year_of_birth,
 74        )
 75
 76        reality = src.person.say_hello(joe)
 77        my_expectation = (
 78            f'Hi, my name is {first_name} {last_name}'
 79            f' and I am {age}'
 80        )
 81        self.assertEqual(reality, my_expectation)
 82
 83        first_name = 'jane'
 84        last_name = 'doe'
 85        year_of_birth = 1991
 86        age = (
 87            datetime.datetime.now().year
 88          - year_of_birth
 89        )
 90
 91        jane = src.person.factory(
 92            sex='F',
 93            first_name=first_name,
 94            year_of_birth=year_of_birth,
 95        )
 96
 97        reality = src.person.say_hello(jane)
 98        my_expectation = (
 99            f'Hi, my name is {first_name} {last_name}'
100            f' and I am {age}'
101        )
102        self.assertEqual(reality, my_expectation)
103
104        first_name = 'john'
105        last_name = 'smith'
106        year_of_birth = 1580
107        age = (
108            datetime.datetime.now().year
109          - year_of_birth
110        )
111
112        john = src.person.factory(
113            first_name=first_name,
114            last_name=last_name,
115            year_of_birth=year_of_birth,
116        )
117
118        reality = src.person.say_hello(john)
119        my_expectation = (
120            f'Hi, my name is {first_name} {last_name}'
121            f' and I am {age}'
122        )
123        self.assertEqual(reality, my_expectation)
124
125        first_name = 'person'
126        last_name = 'public'
127        year_of_birth = 2000
128        age = (
129            datetime.datetime.now().year
130          - year_of_birth
131        )
132
133        a_person = src.person.factory(
134            first_name=first_name,
135            last_name=last_name,
136            year_of_birth=year_of_birth,
137            sex='F',
138        )
139
140        reality = src.person.say_hello(a_person)
141        my_expectation = (
142            f'Hi, my name is {first_name} {last_name}'
143            f' and I am {age}'
144        )
145        self.assertEqual(reality, my_expectation)
146
147
148# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am \
'add test_factory_person_says_hello'

    the terminal shows a summary of the changes then goes back to the command line.

extract calculate_age function

Each assertion in every test has a calculation for the age

  • I go back to the terminal that is running the tests

  • I add a function

    11def get_random_name():
12    return pick_one(
13        'jane', 'joe', 'john', 'person',
14        'doe', 'smith', 'blow', 'public',
15    )
16
17
18def calculate_age(year_of_birth):
19    return (
20        datetime.datetime.now().year
21      - year_of_birth
22    )
23
24
25class TestPerson(unittest.TestCase):
26
27    def test_factory_w_keyword_arguments(self):

  • I use the function to remove repetition of the age calculation from my_expectation in test_factory_w_keyword_arguments

    39        reality = src.person.factory(
40            **a_person,
41            year_of_birth=year_of_birth,
42        )
43        my_expectation = dict(
44            **a_person,
45            # age=this_year-year_of_birth,
46            age=calculate_age(year_of_birth),
47        )
48        self.assertEqual(reality, my_expectation)
49
50    def test_factory_w_optional_arguments(self):

    the test is still green.

  • I remove the commented line

    27    def test_factory_w_keyword_arguments(self):
28        this_year = datetime.datetime.now().year
29        year_of_birth = random.randint(
30            this_year-120, this_year
31        )
32
33        a_person = dict(
34            first_name=get_random_name(),
35            last_name=get_random_name(),
36            sex=pick_one('F', 'M'),
37        )
38
39        reality = src.person.factory(
40            **a_person,
41            year_of_birth=year_of_birth,
42        )
43        my_expectation = dict(
44            **a_person,
45            age=calculate_age(year_of_birth),
46        )
47        self.assertEqual(reality, my_expectation)
48
49    def test_factory_w_optional_arguments(self):

  • I use the function to remove repetition of the age calculation from my_expectation in test_factory_w_optional_arguments

    56        reality = src.person.factory(
57            first_name=first_name,
58            year_of_birth=year_of_birth,
59        )
60        my_expectation = dict(
61            first_name=first_name,
62            last_name='doe',
63            sex='M',
64            # age=this_year-year_of_birth,
65            age=calculate_age(year_of_birth),
66        )
67        self.assertEqual(reality, my_expectation)
68
69    def test_factory_person_says_hello(self):

    the test is still green.

  • I remove the commented line

    49    def test_factory_w_optional_arguments(self):
50        first_name = get_random_name()
51        this_year = datetime.datetime.now().year
52        year_of_birth = random.randint(
53            this_year-120, this_year
54        )
55
56        reality = src.person.factory(
57            first_name=first_name,
58            year_of_birth=year_of_birth,
59        )
60        my_expectation = dict(
61            first_name=first_name,
62            last_name='doe',
63            sex='M',
64            age=calculate_age(year_of_birth),
65        )
66        self.assertEqual(reality, my_expectation)
67
68    def test_factory_person_says_hello(self):

  • I use the function to remove repetition of the age calculation from my_expectation for joe in test_factory_person_says_hello

    68    def test_factory_person_says_hello(self):
69        first_name = 'joe'
70        last_name = 'blow'
71        year_of_birth = 1996
72        # age = (
73        #     datetime.datetime.now().year
74        #   - year_of_birth
75        # )
76
77        joe = src.person.factory(
78            first_name=first_name,
79            last_name=last_name,
80            year_of_birth=year_of_birth,
81        )
82
83        reality = src.person.say_hello(joe)
84        my_expectation = (
85            f'Hi, my name is {first_name} {last_name}'
86            # f' and I am {age}'
87            f' and I am {calculate_age(year_of_birth)}'
88        )
89        self.assertEqual(reality, my_expectation)

    the test is still green.

  • I use the function to remove repetition of the age calculation from my_expectation for jane in test_factory_person_says_hello

     83        reality = src.person.say_hello(joe)
 84        my_expectation = (
 85            f'Hi, my name is {first_name} {last_name}'
 86            # f' and I am {age}'
 87            f' and I am {calculate_age(year_of_birth)}'
 88        )
 89        self.assertEqual(reality, my_expectation)
 90
 91        first_name = 'jane'
 92        last_name = 'doe'
 93        year_of_birth = 1991
 94        # age = (
 95        #     datetime.datetime.now().year
 96        #   - year_of_birth
 97        # )
 98
 99        jane = src.person.factory(
100            sex='F',
101            first_name=first_name,
102            year_of_birth=year_of_birth,
103        )
104
105        reality = src.person.say_hello(jane)
106        my_expectation = (
107            f'Hi, my name is {first_name} {last_name}'
108            # f' and I am {age}'
109            f' and I am {calculate_age(year_of_birth)}'
110        )
111        self.assertEqual(reality, my_expectation)

    still green.

  • I use the function to remove repetition of the age calculation from my_expectation for john in test_factory_person_says_hello

    105        reality = src.person.say_hello(jane)
106        my_expectation = (
107            f'Hi, my name is {first_name} {last_name}'
108            # f' and I am {age}'
109            f' and I am {calculate_age(year_of_birth)}'
110        )
111        self.assertEqual(reality, my_expectation)
112
113        first_name = 'john'
114        last_name = 'smith'
115        year_of_birth = 1580
116        # age = (
117        #     datetime.datetime.now().year
118        #   - year_of_birth
119        # )
120
121        john = src.person.factory(
122            first_name=first_name,
123            last_name=last_name,
124            year_of_birth=year_of_birth,
125        )
126
127        reality = src.person.say_hello(john)
128        my_expectation = (
129            f'Hi, my name is {first_name} {last_name}'
130            # f' and I am {age}'
131            f' and I am {calculate_age(year_of_birth)}'
132        )
133        self.assertEqual(reality, my_expectation)

    green.

  • I use the function to remove repetition of the age calculation from my_expectation for a_person in test_factory_person_says_hello

    127        reality = src.person.say_hello(john)
128        my_expectation = (
129            f'Hi, my name is {first_name} {last_name}'
130            # f' and I am {age}'
131            f' and I am {calculate_age(year_of_birth)}'
132        )
133        self.assertEqual(reality, my_expectation)
134
135        first_name = 'person'
136        last_name = 'public'
137        year_of_birth = 2000
138        # age = (
139        #     datetime.datetime.now().year
140        #   - year_of_birth
141        # )
142
143        a_person = src.person.factory(
144            first_name=first_name,
145            last_name=last_name,
146            year_of_birth=year_of_birth,
147            sex='F',
148        )
149
150        reality = src.person.say_hello(a_person)
151        my_expectation = (
152            f'Hi, my name is {first_name} {last_name}'
153            # f' and I am {age}'
154            f' and I am {calculate_age(year_of_birth)}'
155        )
156        self.assertEqual(reality, my_expectation)
157
158
159# Exceptions seen

    the test is still green.

  • I remove the commented lines

     68    def test_factory_person_says_hello(self):
 69        first_name = 'joe'
 70        last_name = 'blow'
 71        year_of_birth = 1996
 72
 73        joe = src.person.factory(
 74            first_name=first_name,
 75            last_name=last_name,
 76            year_of_birth=year_of_birth,
 77        )
 78
 79        reality = src.person.say_hello(joe)
 80        my_expectation = (
 81            f'Hi, my name is {first_name} {last_name}'
 82            f' and I am {calculate_age(year_of_birth)}'
 83        )
 84        self.assertEqual(reality, my_expectation)
 85
 86        first_name = 'jane'
 87        last_name = 'doe'
 88        year_of_birth = 1991
 89
 90        jane = src.person.factory(
 91            sex='F',
 92            first_name=first_name,
 93            year_of_birth=year_of_birth,
 94        )
 95
 96        reality = src.person.say_hello(jane)
 97        my_expectation = (
 98            f'Hi, my name is {first_name} {last_name}'
 99            f' and I am {calculate_age(year_of_birth)}'
100        )
101        self.assertEqual(reality, my_expectation)
102
103        first_name = 'john'
104        last_name = 'smith'
105        year_of_birth = 1580
106
107        john = src.person.factory(
108            first_name=first_name,
109            last_name=last_name,
110            year_of_birth=year_of_birth,
111        )
112
113        reality = src.person.say_hello(john)
114        my_expectation = (
115            f'Hi, my name is {first_name} {last_name}'
116            f' and I am {calculate_age(year_of_birth)}'
117        )
118        self.assertEqual(reality, my_expectation)
119
120        first_name = 'person'
121        last_name = 'public'
122        year_of_birth = 2000
123
124        a_person = src.person.factory(
125            first_name=first_name,
126            last_name=last_name,
127            year_of_birth=year_of_birth,
128            sex='F',
129        )
130
131        reality = src.person.say_hello(a_person)
132        my_expectation = (
133            f'Hi, my name is {first_name} {last_name}'
134            f' and I am {calculate_age(year_of_birth)}'
135        )
136        self.assertEqual(reality, my_expectation)
137
138
139# Exceptions seen

    the test is still green.

  • I add a git commit message in the other terminal

    git commit -am 'extract calculate_age function'

    the terminal shows a summary of the changes then goes back to the command line.

test_factory_person_says_hello with random values

I want to use random values to test_factory_person_says_hello

  • I go back to the terminal that is running the tests

  • I add random values to use for the first_name, last_name, sex, year_of_birth and age variables

    68    def test_factory_person_says_hello(self):
69        first_name = get_random_name()
70        last_name = get_random_name()
71        sex = pick_one('F', 'M')
72
73        this_year = datetime.datetime.now().year
74        year_of_birth = random.randint(
75            this_year-120, this_year
76        )
77        age = calculate_age(year_of_birth)
78
79        first_name = 'joe'
80        last_name = 'blow'
81        year_of_birth = 1996

  • I comment out the first_name, last_name and year_of_birth variables for joe in the first assertion, so it uses the ones with random values

    68    def test_factory_person_says_hello(self):
69        first_name = get_random_name()
70        last_name = get_random_name()
71        sex = pick_one('F', 'M')
72
73        this_year = datetime.datetime.now().year
74        year_of_birth = random.randint(
75            this_year-120, this_year
76        )
77        age = calculate_age(year_of_birth)
78
79        # first_name = 'joe'
80        # last_name = 'blow'
81        # year_of_birth = 1996
82
83        joe = src.person.factory(
84            first_name=first_name,
85            last_name=last_name,
86            year_of_birth=year_of_birth,
87        )

    the test is still green.

  • I add a random value for the sex parameter with the sex variable in the call to src.person.factory for joe

    83        joe = src.person.factory(
84            first_name=first_name,
85            last_name=last_name,
86            year_of_birth=year_of_birth,
87            sex=sex,
88        )
89
90        reality = src.person.say_hello(joe)
91        my_expectation = (
92            f'Hi, my name is {first_name} {last_name}'
93            f' and I am {calculate_age(year_of_birth)}'
94        )
95        self.assertEqual(reality, my_expectation)

    still green.

  • I use the age variable in my_expectation for joe

    90        reality = src.person.say_hello(joe)
91        my_expectation = (
92            f'Hi, my name is {first_name} {last_name}'
93            # f' and I am {calculate_age(year_of_birth)}'
94            f' and I am {age}'
95        )
96        self.assertEqual(reality, my_expectation)

    green.

  • I comment out the first_name, last_name and year_of_birth variables for jane in the second assertion, so it uses the ones with random values

     89        reality = src.person.say_hello(joe)
 90        my_expectation = (
 91            f'Hi, my name is {first_name} {last_name}'
 92            # f' and I am {calculate_age(year_of_birth)}'
 93            f' and I am {age}'
 94        )
 95        self.assertEqual(reality, my_expectation)
 96
 97        # first_name = 'jane'
 98        # last_name = 'doe'
 99        # year_of_birth = 1991
100
101        jane = src.person.factory(
102            sex='F',
103            first_name=first_name,
104            year_of_birth=year_of_birth,
105        )

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes if the last_name is randomly 'doe'.

    If the last_name is not 'doe', the terminal is my friend, and shows AssertionError

    AssertionError:
    'Hi, my name is X doe and I am Z'
 != 'Hi, my name is X Y and I am Z'

    because I did not need to give a value for the last_name parameter in the call to src.person.factory since the default value for the last_name parameter of the function is 'doe'. This means that

    src.person.factory(
    sex='F',
    first_name=first_name,
    year_of_birth=year_of_birth,
)

    is the same as

    src.person.factory(
    sex='F',
    first_name=first_name,
    year_of_birth=year_of_birth,
    last_name='doe'
)

    because a function uses the default value for a parameter when it is called without the parameter.

  • I add last_name to the call to src.person.factory for jane to use the variable

    102        jane = src.person.factory(
103            sex='F',
104            first_name=first_name,
105            last_name=last_name,
106            year_of_birth=year_of_birth,
107        )

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and it passes with no more random failures.

  • I change the value for the sex parameter to the sex variable so it uses a random value in the call to src.person.factory for jane

    102        jane = src.person.factory(
103            # sex='F',
104            first_name=first_name,
105            last_name=last_name,
106            year_of_birth=year_of_birth,
107            sex=sex,
108        )

    the test is still green.

  • I use the age variable in my_expectation for jane

    110        reality = src.person.say_hello(jane)
111        my_expectation = (
112            f'Hi, my name is {first_name} {last_name}'
113            # f' and I am {calculate_age(year_of_birth)}'
114            f' and I am {age}'
115        )
116        self.assertEqual(reality, my_expectation)

    still green.

  • I comment out the first_name, last_name and year_of_birth variables for john in the third assertion, so it uses the ones with random values

    110        reality = src.person.say_hello(jane)
111        my_expectation = (
112            f'Hi, my name is {first_name} {last_name}'
113            # f' and I am {calculate_age(year_of_birth)}'
114            f' and I am {age}'
115        )
116        self.assertEqual(reality, my_expectation)
117
118        # first_name = 'john'
119        # last_name = 'smith'
120        # year_of_birth = 1580
121
122        john = src.person.factory(
123            first_name=first_name,
124            last_name=last_name,
125            year_of_birth=year_of_birth,
126        )

    green.

  • I add a random value for the sex parameter with the sex variable in the call to src.person.factory for john

    122        john = src.person.factory(
123            first_name=first_name,
124            last_name=last_name,
125            year_of_birth=year_of_birth,
126            sex=sex,
127        )

    still green.

  • I use the age variable in my_expectation for john

    129        reality = src.person.say_hello(john)
130        my_expectation = (
131            f'Hi, my name is {first_name} {last_name}'
132            # f' and I am {calculate_age(year_of_birth)}'
133            f' and I am {age}'
134        )
135        self.assertEqual(reality, my_expectation)

    the test is still green.

  • I comment out the first_name, last_name and year_of_birth variables for a_person in the last assertion, so it uses the ones with random values

    129        reality = src.person.say_hello(john)
130        my_expectation = (
131            f'Hi, my name is {first_name} {last_name}'
132            # f' and I am {calculate_age(year_of_birth)}'
133            f' and I am {age}'
134        )
135        self.assertEqual(reality, my_expectation)
136
137        # first_name = 'person'
138        # last_name = 'public'
139        # year_of_birth = 2000
140
141        a_person = src.person.factory(
142            first_name=first_name,
143            last_name=last_name,
144            year_of_birth=year_of_birth,
145            sex='F',
146        )

    still green.

  • I add a random value for the sex parameter with the sex variable in the call to src.person.factory for a_person

    141        a_person = src.person.factory(
142            first_name=first_name,
143            last_name=last_name,
144            year_of_birth=year_of_birth,
145            # sex='F',
146            sex=sex,
147        )

    green.

  • I use the age variable in my_expectation for a_person

    149    reality = src.person.say_hello(a_person)
150    my_expectation = (
151        f'Hi, my name is {first_name} {last_name}'
152        # f' and I am {calculate_age(year_of_birth)}'
153        f' and I am {age}'
154    )
155    self.assertEqual(reality, my_expectation)

    still green.

  • I add a random person for the four people I made in test_factory_person_says_hello because they all now all use the same random values. The assertions are also the same for each case because they use the first_name, last_name and age variables that are sent in the call to src.person.factory

    149        reality = src.person.say_hello(a_person)
150        my_expectation = (
151            f'Hi, my name is {first_name} {last_name}'
152            # f' and I am {calculate_age(year_of_birth)}'
153            f' and I am {age}'
154        )
155        self.assertEqual(reality, my_expectation)
156
157        a_random_person = src.person.factory(
158            first_name=first_name,
159            last_name=last_name,
160            sex=sex,
161            year_of_birth=year_of_birth,
162        )
163
164        reality = src.person.say_hello(a_random_person)
165        my_expectation = ''
166        self.assertEqual(reality, my_expectation)
167
168
169# Exceptions seen

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times, and each time the terminal shows AssertionError

    AssertionError: 'Hi, my name is Z Y and I am X' != ''

    where X is a random age, Z is a random last name and Y is a random first name

  • I change my_expectation to match reality for a_random_person

    157        a_random_person = src.person.factory(
158            first_name=first_name,
159            last_name=last_name,
160            sex=sex,
161            year_of_birth=year_of_birth,
162        )
163
164        reality = src.person.say_hello(a_random_person)
165        my_expectation = (
166            f'Hi, my name is {first_name} {last_name}'
167            f' and I am {age}'
168        )
169        self.assertEqual(reality, my_expectation)
170
171
172# Exceptions seen

    the test passes.

  • I remove the commented lines and joe, jane, john and person from test_factory_person_says_hello because they are all the same as a_random_person

    68    def test_factory_person_says_hello(self):
69        first_name = get_random_name()
70        last_name = get_random_name()
71        sex = pick_one('F', 'M')
72
73        this_year = datetime.datetime.now().year
74        year_of_birth = random.randint(
75            this_year-120, this_year
76        )
77        age = calculate_age(year_of_birth)
78
79        a_random_person = src.person.factory(
80            first_name=first_name,
81            last_name=last_name,
82            sex=sex,
83            year_of_birth=year_of_birth,
84        )
85
86        reality = src.person.say_hello(a_random_person)
87        my_expectation = (
88            f'Hi, my name is {first_name} {last_name}'
89            f' and I am {age}'
90        )
91        self.assertEqual(reality, my_expectation)
92
93
94# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am \
'test_factory_person_says_hello with random values'

    the terminal shows a summary of the changes then goes back to the command line.

extract get_random_year_of_birth function

I make the this_year and year_of_birth variables the same way in all three tests.

  • I go back to the terminal that is running the tests

  • I add a function to use to replace the repetition of making the values for the this_year and year_of_birth variables in test_person.py

    18def calculate_age(year_of_birth):
19    return (
20        datetime.datetime.now().year
21      - year_of_birth
22    )
23
24
25def get_random_year_of_birth():
26    this_year = datetime.datetime.now().year
27    return random.randint(
28        this_year-120, this_year
29    )
30
31
32class TestPerson(unittest.TestCase):
33
34    def test_factory_w_keyword_arguments(self):

  • I use the get_random_year_of_birth function to replace the repetition of making the values for the this_year and year_of_birth variables in test_factory_w_keyword_arguments

    34    def test_factory_w_keyword_arguments(self):
35        # this_year = datetime.datetime.now().year
36        # year_of_birth = random.randint(
37        #     this_year-120, this_year
38        # )
39        year_of_birth = get_random_year_of_birth()

    the test is still green.

  • I remove the commented lines

    34    def test_factory_w_keyword_arguments(self):
35        year_of_birth = get_random_year_of_birth()
36
37        a_person = dict(
38            first_name=get_random_name(),
39            last_name=get_random_name(),
40            sex=pick_one('F', 'M'),
41        )
42
43        reality = src.person.factory(
44            **a_person,
45            year_of_birth=year_of_birth,
46        )
47        my_expectation = dict(
48            **a_person,
49            age=calculate_age(year_of_birth),
50        )
51        self.assertEqual(reality, my_expectation)
52
53    def test_factory_w_optional_arguments(self):

  • I use the get_random_year_of_birth function to replace the repetition of making the values for the this_year and year_of_birth variables in test_factory_w_optional_arguments

    53    def test_factory_w_optional_arguments(self):
54        first_name = get_random_name()
55        # this_year = datetime.datetime.now().year
56        # year_of_birth = random.randint(
57        #     this_year-120, this_year
58        # )
59        year_of_birth = get_random_year_of_birth()

    the test is still green.

  • I remove the commented lines

    53    def test_factory_w_optional_arguments(self):
54        first_name = get_random_name()
55        year_of_birth = get_random_year_of_birth()
56
57        reality = src.person.factory(
58            first_name=first_name,
59            year_of_birth=year_of_birth,
60        )
61        my_expectation = dict(
62            first_name=first_name,
63            last_name='doe',
64            sex='M',
65            age=calculate_age(year_of_birth),
66        )
67        self.assertEqual(reality, my_expectation)
68
69    def test_factory_person_says_hello(self):

  • I use the get_random_year_of_birth function to replace the repetition of making the values for the this_year and year_of_birth variables in test_factory_person_says_hello

    69    def test_factory_person_says_hello(self):
70        first_name = get_random_name()
71        last_name = get_random_name()
72        sex = pick_one('F', 'M')
73
74        # this_year = datetime.datetime.now().year
75        # year_of_birth = random.randint(
76        #     this_year-120, this_year
77        # )
78        year_of_birth = get_random_year_of_birth()
79        age = calculate_age(year_of_birth)

    the test is still green.

  • I remove the commented lines

    69    def test_factory_person_says_hello(self):
70        first_name = get_random_name()
71        last_name = get_random_name()
72        sex = pick_one('F', 'M')
73
74        year_of_birth = get_random_year_of_birth()
75        age = calculate_age(year_of_birth)
76
77        a_random_person = src.person.factory(
78            first_name=first_name,
79            last_name=last_name,
80            sex=sex,
81            year_of_birth=year_of_birth,
82        )
83
84        reality = src.person.say_hello(a_random_person)
85        my_expectation = (
86            f'Hi, my name is {first_name} {last_name}'
87            f' and I am {age}'
88        )
89        self.assertEqual(reality, my_expectation)
90
91
92# Exceptions seen
93# AssertionError
94# NameError
95# AttributeError
96# TypeError
97# SyntaxError

  • I add a git commit message in the other terminal

    git commit -am \
'extract get_random_year_of_birth function'

    the terminal shows a summary of the changes then goes back to the command line.

test_person_tests

I want to write the solution without looking at the tests

RED: make it fail

  • I go back to the terminal that is running the tests

  • I close test_person.py

  • then I delete all the text in person.py, the terminal is my friend, and shows AttributeError

    FAILED ...test_factory_person_says_hello -
    AttributeError: module 'src.person' has
                    no attribute 'factory'
FAILED ...test_factory_w_keyword_arguments -
    AttributeError: module 'src.person' has
                    no attribute 'factory'
FAILED ...test_factory_w_optional_arguments -
    AttributeError: module 'src.person' has
                    no attribute 'factory'

    because there is nothing in person.py with the name factory

GREEN: make it pass

  • I add the name

    1factory

    the terminal is my friend, and shows NameError

    NameError: name 'factory' is not defined

    because I have not told Python what factory means

  • I point it to None to define it

    1# factory
2factory = None

    the terminal is my friend, and shows TypeError

    TypeError: 'NoneType' object is not callable

    because factory points to None and I cannot call None like a function

  • I make factory a function to make it callable

    1# factory
2# factory = None
3def factory():
4    return None

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'first_name'

    because the test called the factory function with a keyword argument (first_name) that is not in the function definition

  • I add first_name to the function definition

    1# factory
2# factory = None
3# def factory():
4def factory(first_name):
5    return None

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'year_of_birth'

    because the test called the factory function with a keyword argument (year_of_birth) that is not in the function definition

  • I add year_of_birth to the function definition

    1# factory
2# factory = None
3# def factory():
4# def factory(first_name):
5def factory(first_name, year_of_birth):
6    return None

    the terminal is my friend, and shows AssertionError

    AssertionError: None != {'first_name': Y,
                         'last_name': 'doe',
                         'sex': 'M', 'age': X}

    because the assertion expects a dictionary and the factory function returns None

  • I copy and paste the dictionary from the terminal to make the function return a dictionary instead of None

     1# factory
 2# factory = None
 3# def factory():
 4# def factory(first_name):
 5def factory(first_name, year_of_birth):
 6    # return None
 7    return {
 8        'first_name': 'john',
 9        'last_name': 'doe',
10        'sex': 'M',
11        'age': 55,
12    }

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and the terminal shows AssertionError

    AssertionError:
    {'first_name': A, 'last_name': 'doe',
     'sex': 'M', 'age': Y}
 != {'first_name': Z, 'last_name': 'doe',
     'sex': 'M', 'age': X}

    the values of the age and first_name keys change randomly

  • I use the first_name input parameter in the return statement

     1# factory
 2# factory = None
 3# def factory():
 4# def factory(first_name):
 5def factory(first_name, year_of_birth):
 6    # return None
 7    return {
 8        # 'first_name': 'john',
 9        'first_name': first_name,
10        'last_name': 'doe',
11        'sex': 'M',
12        'age': 55,
13    }

    the first name matches and if the ages are different, the terminal shows AssertionError

    AssertionError:
    {'first_name': Z, 'last_name': 'doe',
     'sex': 'M', 'age': Y}
 != {'first_name': Z, 'last_name': 'doe',
     'sex': 'M', 'age': X}

    and TypeError

    TypeError: factory() got
           an unexpected keyword argument 'last_name'.
           Did you mean 'first_name'?

  • I use the year_of_birth input parameter in the return statement for the value of age

     1# factory
 2# factory = None
 3# def factory():
 4# def factory(first_name):
 5def factory(first_name, year_of_birth):
 6    # return None
 7    return {
 8        # 'first_name': 'john',
 9        'first_name': first_name,
10        'last_name': 'doe',
11        'sex': 'M',
12        # 'age': 55,
13        'age': year_of_birth,
14    }

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': Y, 'last_name': 'doe',
     'sex': 'M', 'age': ABCD}
 != {'first_name': Y, 'last_name': 'doe',
     'sex': 'M', 'age': X}

    because the factory function returned 4 digits (a year) as the value for the age key, and the assertion expects the difference between that value and the current year

  • I add an import statement for the datetime module at the top of the file

    1import datetime
2
3
4
5# factory
6# factory = None
7# def factory():
8# def factory(first_name):
9def factory(first_name, year_of_birth):

    the terminal still shows AssertionError

  • I use the datetime module to get the current year, then use it for the age calculation

     9def factory(first_name, year_of_birth):
10    # return None
11    return {
12        # 'first_name': 'john',
13        'first_name': first_name,
14        'last_name': 'doe',
15        'sex': 'M',
16        # 'age': 55,
17        # 'age': year_of_birth,
18        'age': (
19            datetime.datetime.today().year
20          - year_of_birth
21        ),
22    }

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'last_name'.
           Did you mean 'first_name'?

    because the test called the factory function with a keyword argument (last_name) that is not in the function definition

  • I add a new input parameter to the function

     9# def factory(first_name, year_of_birth):
10def factory(
11        first_name, year_of_birth,
12        last_name,
13    ):

    the terminal is my friend, and shows TypeError

    TypeError: factory() missing 1 required
           positional argument: 'last_name'

    because the test called the function with another argument and Python took that argument as a positional argument for last_name

  • I add a default value for last_name so Python does not take it is a positional argument when a name is not given

    10def factory(
11        first_name, year_of_birth,
12        # last_name,
13        last_name=None,
14    ):

    the terminal is my friend, and shows TypeError

    TypeError: factory() got
           an unexpected keyword argument 'sex'

    because the test called the factory function with a keyword argument (sex) that is not in the function definition

  • I add the name to the definition of the function

    10def factory(
11        first_name, year_of_birth,
12        # last_name,
13        # last_name=None,
14        last_name=None, sex,
15    ):

    the terminal is my friend, and shows SyntaxError

    SyntaxError: parameter without a default follows
             parameter with a default

    because parameters without default values must come before parameters with default values

  • I add a default value for sex to make it optional

    10def factory(
11        first_name, year_of_birth,
12        # last_name,
13        # last_name=None,
14        # last_name=None, sex,
15        last_name=None, sex=None,
16    ):

    the terminal is my friend, and shows AssertionError first_name and age match. If the last names are different, the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': C, 'last_name': B, 'sex': Z, 'age': X}
 != {'first_name': C, 'last_name': A, 'sex': Y, 'age': X}

    and AttributeError

    AttributeError: module 'src.person'
                has no attribute 'say_hello'

  • I use the sex input parameter in the return statement

    10def factory(
11        first_name, year_of_birth,
12        # last_name,
13        # last_name=None,
14        # last_name=None, sex,
15        last_name=None, sex=None,
16    ):
17    # return None
18    return {
19        # 'first_name': 'john',
20        'first_name': first_name,
21        'last_name': 'doe',
22        # 'sex': 'M',
23        'sex': sex,
24        # 'age': 55,
25        # 'age': year_of_birth,
26        'age': (
27            datetime.datetime.today().year
28          - year_of_birth
29        ),
30    }

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': Y, 'last_name': 'doe',
     'sex': None, 'age': X}
 != {'first_name': Y, 'last_name': 'doe',
     'sex': 'M', 'age': X}

    because the assertion expects 'M' as the value of sex and the function returns None which is its default value

  • I change the default value of sex to 'M'

    10def factory(
11    first_name, year_of_birth,
12    # last_name,
13    # last_name=None,
14    # last_name=None, sex,
15    # last_name=None, sex=None,
16    last_name=None, sex='M',
17):

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times and if the last_name is not 'doe', the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': A, 'last_name': 'doe', 'sex': Y, 'age': X}
 != {'first_name': A, 'last_name': Z, 'sex': Y, 'age': X}

    because the last_name value is different between the two dictionaries. It still shows AttributeError

    AttributeError: module 'src.person'
                has no attribute 'say_hello'

  • I use the last_name input parameter in the return statement

     4def factory(
 5        first_name, year_of_birth,
 6        # last_name,
 7        # last_name=None,
 8        # last_name=None, sex,
 9        # last_name=None, sex=None,
10        last_name=None, sex='M',
11    ):
12    # return None
13    return {
14        # 'first_name': 'john',
15        'first_name': first_name,
16        # 'last_name': 'doe',
17        'last_name': last_name,
18        # 'sex': 'M',
19        'sex': sex,
20        # 'age': 55,
21        # 'age': year_of_birth,
22        'age': (
23            datetime.datetime.today().year
24          - year_of_birth
25        ),
26    }

    the terminal is my friend, and shows AssertionError

    AssertionError:
    {'first_name': Z, 'last_name': None,
     'sex': Y, 'age': X}
 != {'first_name': Z, 'last_name': 'doe',
     'sex': Y, 'age': X}

    because the assertion expects 'doe' as the value of last_name and the function returns None which is its default value

  • I change the default value for last_name to match the expectation

    10def factory(
11        first_name, year_of_birth,
12        # last_name,
13        # last_name=None,
14        # last_name=None, sex,
15        # last_name=None, sex=None,
16        # last_name=None, sex='M',
17        last_name='doe', sex='M',
18    ):

    the terminal is my friend, and shows AttributeError

    AttributeError: module 'src.person'
                has no attribute 'say_hello'

    because I do not have a definition for say_hello

  • I add say_hello

     1import datetime
 2
 3
 4say_hello
 5
 6
 7# factory
 8# factory = None
 9# def factory():
10# def factory(first_name):
11# def factory(first_name, year_of_birth):
12def factory(

    the terminal is my friend, and shows NameError

    NameError: name 'say_hello' is not defined

  • I point it to None to define it

    1import datetime
2
3
4# say_hello
5say_hello = None
6
7
8# factory

    the terminal is my friend, and shows TypeError

    TypeError: 'NoneType' object is not callable

    because say_hello points to None and I cannot call None like a function

  • I make say_hello a function to make it callable

     1import datetime
 2
 3
 4# say_hello
 5# say_hello = None
 6def say_hello():
 7    return None
 8
 9
10# factory

    the terminal is my friend, and shows TypeError

    TypeError: say_hello() takes 0 positional arguments
           but 1 was given

    because the function definition for say_hello does not allow calling it with inputs (the parentheses are empty) and the test sends input.

  • I add a name to the function definition

    4# say_hello
5# say_hello = None
6# def say_hello():
7def say_hello(argument):
8    return None

    the terminal is my friend, and shows AssertionError

    AssertionError: None != 'Hi, my name is Z Y and I am Z'

    because the test expects a string and the say_hello function returns None

  • I copy (ctrl/command+c) the string from the terminal and paste it (ctrl/command+v) to replace the return statement

     4# say_hello
 5# say_hello = None
 6# def say_hello():
 7def say_hello(argument):
 8    # return None
 9    return 'Hi, my name is jade doe and I am 66'
10
11
12# factory

    I use ctrl+s (Windows/Linux) or command+s (MacOS) to run the test a few times, and the terminal shows AssertionError

    AssertionError:
    'Hi, my name is Z Y and I am X'
 != 'Hi, my name is A B and I am C'

    the names and ages change

  • I return the input to compare it with what the test expects

     4# say_hello
 5# say_hello = None
 6# def say_hello():
 7def say_hello(argument):
 8    # return None
 9    return argument
10    return 'Hi, my name is jade doe and I am 66'

    the terminal shows AssertionError

    AssertionError:
    {'first_name': A, 'last_name': Z, 'sex': Y, 'age': X}
!= 'Hi, my name is A Z and I am X'

    the test sends a dictionary as input and expects a string as output, and the string uses the values of the first_name, last_name and age keys from the dictionary it receives

  • I return an f-string with the values of the first_name, last_name and age keys from the dictionary

     4# say_hello
 5# say_hello = None
 6# def say_hello():
 7def say_hello(argument):
 8    # return None
 9    return (
10        f'Hi, my name is {argument.get("first_name")}'
11        f' {argument.get("last_name")}'
12        f' and I am {argument.get("age")}'
13    )
14    return argument
15    return 'Hi, my name is jade doe and I am 66'

    the test passes. Okay!

REFACTOR: make it better

  • I use the Rename Symbol feature of the Integrated Development Environment (IDE) to change argument to make it clearer

     4# say_hello
 5# say_hello = None
 6# def say_hello():
 7def say_hello(a_dictionary):
 8    # return None
 9    return (
10        f'Hi, my name is {a_dictionary.get("first_name")}'
11        f' {a_dictionary.get("last_name")}'
12        f' and I am {a_dictionary.get("age")}'
13    )
14    return a_dictionary
15    return 'Hi, my name is jade doe and I am 66'

  • I remove the commented lines and other return statements

     1import datetime
 2
 3
 4def say_hello(a_dictionary):
 5    return (
 6        f'Hi, my name is {a_dictionary.get("first_name")}'
 7        f' {a_dictionary.get("last_name")}'
 8        f' and I am {a_dictionary.get("age")}'
 9    )
10
11
12def factory(
13        first_name, year_of_birth,
14        last_name='doe', sex='M',
15    ):
16    return {
17        'first_name': first_name,
18        'last_name': last_name,
19        'sex': sex,
20        'age': (
21            datetime.datetime.today().year
22          - year_of_birth
23        ),
24    }

    This factory function only has two parameters with default values (last_name and sex)

    def factory(
        first_name, year_of_birth,
        last_name='doe', sex='M',
    ):

    the first solution had three parameters with default values (last_name, sex and year_of_birth)

    def factory(
        first_name, last_name='doe',
        sex='M', year_of_birth=None,
    ):

    I can learn new things from repetition.

  • I add a git commit message in the other terminal

    git commit -am \
'refactor factory and say_hello functions'

    the terminal shows a summary of the changes then goes back to the command line.

close the project

  • I close person.py

  • I click in the terminal where the tests are running

  • I use q on the keyboard to leave the tests. The terminal goes back to the command line.

  • I change directory to the parent of person

    cd ..

    the terminal shows

    ...\pumping_python

    I am back in the pumping_python directory

review

I ran tests to make

I also saw these Exceptions

code from the chapter

Do you want to see all the CODE I typed in this chapter?

what is next?

you know:

Would you like to see another way to make a person?

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