telephone

Part of Computer Programming is sending input data to a process and getting output data back

input_object -> process -> output_object

I send things (input data) to a program to test it, and check if what I think will happen (my expectation) is the same as the results I get (reality). This helps me answer two questions:

  • what is the same?

  • what is different?

The difference helps me know what to change to get what I want. I use assertions to test if the result of a call to a function with input is the same as my expectation.

assert reality == my_expectation

where

  • reality is what happens when I do something with code

  • my expectation is what I think will happen when I do something with code

The exercises in this chapter show how I can pass objects to a function and use it to make a string (anything in quotes).

preview

I have these tests by the end of the chapter

 1def text(the_input):
 2    return f'I got: {the_input}'
 3
 4
 5def test_passing_none():
 6    assert text(None) == 'I got: None'
 7
 8
 9def test_passing_booleans():
10    assert text(False) == 'I got: False'
11    assert text(True) == 'I got: True'
12
13
14def test_passing_an_integer():
15    an_integer = 1234
16    assert text(an_integer) == f'I got: {an_integer}'
17
18
19def test_passing_a_float():
20    a_float = 5.678
21    assert text(a_float) == f'I got: {a_float}'
22
23
24def test_passing_a_string():
25    a_string = 'hello'
26    assert text(a_string) == f'I got: {a_string}'
27
28
29def test_passing_a_tuple():
30    a_tuple = (0, 1, 2, 'n')
31    assert text(a_tuple) == f'I got: {a_tuple}'
32
33
34def test_passing_a_list():
35    a_list = [0, 1, 2, 'n']
36    assert text(a_list) == f'I got: {a_list}'
37
38
39def test_passing_a_set():
40    a_set = {0, 1, 2, 'n'}
41    assert text(a_set) == f"I got: {a_set}"
42
43
44def test_passing_a_dictionary():
45    a_dictionary = {
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    }
49    reality = text(a_dictionary)
50    my_expectation = f'I got: {a_dictionary}'
51    assert reality == my_expectation
52
53
54def test_passing_a_class():
55    assert text(object) == "I got: <class 'object'>"
56    assert text(bool) == "I got: <class 'bool'>"
57    assert text(int) == "I got: <class 'int'>"
58    assert text(float) == "I got: <class 'float'>"
59    assert text(str) == "I got: <class 'str'>"
60    assert text(tuple) == "I got: <class 'tuple'>"
61    assert text(list) == "I got: <class 'list'>"
62    assert text(set) == "I got: <class 'set'>"
63    assert text(dict) == "I got: <class 'dict'>"
64
65
66# Exceptions seen
67# AssertionError
68# NameError
69# TypeError

start the project

  • I name this project telephone

  • I open a terminal

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

    uv init telephone

    the terminal shows

    Initialized project `telephone`
at `.../pumping_python/telephone`

    then goes back to the command line.

  • I change directory to the project

    cd telephone

    the terminal shows I am in the telephone folder

    .../pumping_python/telephone

  • 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 use the mv program to change the name of main.py to test_telephone.py and move it to the tests folder

    mv main.py tests/test_telephone.py

    Move-Item main.py tests/test_telephone.py

    the terminal goes back to the command line.

  • I open test_telephone.py

  • I delete all the text then add the first failing test to test_telephone.py

    1def test_failure():
2    assert False is True

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

    echo "pytest" > requirements.txt

    the terminal goes back to the command line.

  • I add pytest-watcher to the requirements file

    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 --all --message 'setup project'

    the terminal shows

    [main (root-commit) a0b12c3] setup project
 8 files changed, X 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 tests/__init__.py
 create mode 100644 tests/test_telephone.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 ========================
______________________ test_failure ______________________

    def test_failure():
>       assert False is True
E       assert False is True

test_telephone.py:2: AssertionError
================ short test summary info =================
FAILED test_telephone.py::test_failure - assert False is True
=================== 1 failed in X.YZs ====================

    because False is NOT True.

    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

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

    and try uv run pytest-watcher . --now again

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

    1def test_failure():
2    assert False is True
3
4
5# Exceptions seen
6# AssertionError

  • I change True to False in the assertion

    1def test_failure():
2    # assert False is True
3    assert False is False
4
5
6# Exceptions seen
7# AssertionError

    the test passes.

test_passing_none

Can I pass None (the simplest object) as input to a function?

RED: make it fail

GREEN: make it pass

  • I add the function

    1def test_passing_none():
2    def text():
3        return None
4
5    assert text(None) == 'I got: None'
6
7
8# Exceptions seen

    the terminal is my friend, and shows TypeError

    TypeError: test_passing_none.<locals>.text()
           takes 0 positional arguments but 1 was given

    because the assertion called the text function which belongs to test_passing_none with input (None) and the function definition does not allow any inputs, the parentheses are empty.

  • I add TypeError to the list of Exceptions seen

     8# Exceptions seen
 9# AssertionError
10# NameError
11# TypeError

  • I add a name to the function definition

    1def test_passing_none():
2    # def text():
3    def text(the_input):
4        return None
5
6    assert text(None) == 'I got: None'
7
8
9# Exceptions seen

    • the_input is the name I used for the input, I can use any name I want.

    • the terminal is my friend, and shows AssertionError

      E       assert None == 'I got: None'

    because the assertion expects 'I got: None' and the text function returns None.

  • I copy the string from the terminal and paste it in the return statement to replace None

     1def test_passing_none():
 2    # def text():
 3    def text(the_input):
 4        # return None
 5        return 'I got: None'
 6
 7    assert text(None) == 'I got: None'
 8
 9
10# Exceptions seen

    the test passes.

REFACTOR: make it better

  • I remove the commented lines

    1def test_passing_none():
2    def text(the_input):
3        return 'I got: None'
4
5    assert text(None) == 'I got: None'
6
7
8# Exceptions seen

  • I open a new terminal then change directories to telephone

    cd telephone

    the terminal shows I am in the telephone folder

    .../pumping_python/telephone

  • I add a git commit message in the new terminal

    git commit -am 'add test_passing_none'

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

I can pass None as input to a function.

The problem with this solution is that the text function does not care about what it gets, it always returns 'I got: None' when it is called. I want it to return the object it gets as part of the string.

test_passing_booleans

Can I pass booleans from a test to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for booleans (there are only two), first with an assertion for False

     1def test_passing_none():
 2    def text(the_input):
 3        return 'I got: None'
 4
 5    assert text(None) == 'I got: None'
 6
 7
 8def test_passing_booleans():
 9    assert text(False) == 'I got: False'
10
11
12# Exceptions seen

    the terminal is my friend, and shows NameError

    NameError: name 'text' is not defined

    because the text function belongs to the test_passing_none function and I cannot reach it from outside.

GREEN: make it pass

  • I move the text function out of test_passing_none so that it can be called from anywhere in the file

    1def text(the_input):
2    return 'I got: None'
3
4
5def test_passing_none():
6    assert text(None) == 'I got: None'
7
8
9def test_passing_booleans():

    the terminal is my friend, and shows AssertionError

    AssertionError: assert 'I got: None'
                    == 'I got: False'

    because the text function always returns 'I got: None' and this assertion expects 'I got: False'.

  • I change the return statement to give the test what it wants

    1def text(the_input):
2    # return 'I got: None'
3    return 'I got: False'
4
5
6def test_passing_none():

    the terminal is my friend, and shows AssertionError

    AssertionError: assert 'I got: False' == 'I got: None'

what is string interpolation?

String Interpolation is how to place objects in strings. It allows me to make one string that can have values that change.

I can use an f-string (short for formatted string literal) for string interpolation.

A string is anything inside quotes, for example

  • 'single quotes'

  • '''triple single quotes'''

  • "double quotes"

  • """triple double quotes"""

how to write an f-string

f'characters {object} more characters'

  • I add the_input to the string in the return statement

    1def text(the_input):
2    # return 'I got: None'
3    # return 'I got: False'
4    return 'I got: {the_input}'

    the terminal is my friend, and shows AssertionError

    AssertionError: assert 'I got: {the_input}'
                    == 'I got: False'

  • I change the return statement to an f-string

    1def text(the_input):
2    # return 'I got: None'
3    # return 'I got: False'
4    # return 'I got: {the_input}'
5    return f'I got: {the_input}'
6
7
8def test_passing_none():

    the test passes because Python uses the string representation of the object in the curly braces { }

    text(None)
    text(the_input)
        the_input = None
        return f'I got: {the_input}'
        return  'I got:  None      '

    text(False)
    text(the_input)
        the_input = False
        return f'I got: {the_input}'
        return  'I got:  False     '

REFACTOR: make it better

  • I remove the commented lines

    1def text(the_input):
2    return f'I got: {the_input}'
3
4
5def test_passing_none():

  • I add an assertion for True (the other boolean) to test_passing_booleans

     9def test_passing_booleans():
10    assert text(False) == 'I got: False'
11    assert text(True) == 'I got: "True"'
12
13
14# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert 'I got: True'
            == 'I got: "True"

  • I remove the quotes around True in my expectation

     9def test_passing_booleans():
10    assert text(False) == 'I got: False'
11    # assert text(True) == 'I got: "True"'
12    assert text(True) == 'I got: True'
13
14
15# Exceptions seen

    the test passes because Python uses the string representation of the object in the curly braces { }

    text(True)
    text(the_input)
        the_input = True
        return f'I got: {the_input}'
        return  'I got:  True      '

  • I remove the commented line

     9def test_passing_booleans():
10    assert text(False) == 'I got: False'
11    assert text(True) == 'I got: True'
12
13
14# Exceptions seen

  • I add a git commit message in the other terminal

    git commit --all --message \
'add test_passing_booleans'

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

I can pass booleans as input to a function.

test_passing_an_integer

Can I pass an integer (a whole number without decimals) as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for an integer

     9def test_passing_booleans():
10    assert text(False) == 'I got: False'
11    assert text(True) == 'I got: True'
12
13
14def test_passing_an_integer():
15    assert text(1234) == 'I got: "1234"'
16
17
18# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert 'I got: 1234'
            == 'I got: "1234"'

GREEN: make it pass

I remove the quotes around the integer in my expectation

14def test_passing_an_integer():
15    # assert text(1234) == 'I got: "1234"'
16    assert text(1234) == 'I got: 1234'
17
18
19# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text(1234)
    text(the_input)
        the_input = 1234
        return f'I got: {the_input}'
        return  'I got:  1234      '

REFACTOR: make it better

  • I add a variable for 1234

    14def test_passing_an_integer():
15    an_integer = 1234
16    # assert text(1234) == 'I got: "1234"'
17    assert text(1234) == 'I got: 1234'
18
19
20# Exceptions seen

  • I use the variable and an f-string to remove repetition of 1234

    14def test_passing_an_integer():
15    an_integer = 1234
16    # assert text(1234) == 'I got: "1234"'
17    # assert text(1234) == 'I got: 1234'
18    assert text(an_integer) == f'I got: {an_integer}'
19
20
21# Exceptions seen

    the test is still green.

  • I remove the commented lines

    14def test_passing_an_integer():
15    an_integer = 1234
16    assert text(an_integer) == f'I got: {an_integer}'
17
18
19# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am 'add test_passing_an_integer'

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

I can pass an integer as input to a function.

test_passing_a_float

Can I pass a float (binary floating point decimal number) as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a float (binary floating point decimal numbers)

    14def test_passing_an_integer():
15    an_integer = 1234
16    assert text(an_integer) == f'I got: {an_integer}'
17
18
19def test_passing_a_float():
20    assert text(5.678) == 'I got: "5.678"'
21
22
23# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert 'I got: 5.678'
            == 'I got: "5.678"'

GREEN: make it pass

I remove the quotes around the float in my expectation

19def test_passing_a_float():
20    # assert text(5.678) == 'I got: "5.678"'
21    assert text(5.678) == 'I got: 5.678'
22
23
24# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text(5.678)
    text(the_input)
        the_input = 5.678
        return f'I got: {the_input}'
        return  'I got:  5.678     '

REFACTOR: make it better

  • I add a variable for 5.678

    19def test_passing_a_float():
20    a_float = 5.678
21    # assert text(5.678) == 'I got: "5.678"'
22    assert text(5.678) == 'I got: 5.678'
23
24
25# Exceptions seen

  • I use the variable and an f-string to remove repetition of 5.678

    19def test_passing_a_float():
20    a_float = 5.678
21    # assert text(5.678) == 'I got: "5.678"'
22    # assert text(5.678) == 'I got: 5.678'
23    assert text(a_float) == f'I got: {a_float}'
24
25
26# Exceptions seen

    the test is still green.

  • I remove the commented lines

    19def test_passing_a_float():
20    a_float = 5.678
21    assert text(a_float) == f'I got: {a_float}'
22
23
24# Exceptions seen

  • I add a git commit message in the other terminal

    git commit --all --message \
'add test_passing_a_float'

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

I can pass a float as input to a function.

test_passing_a_string

Can I pass a string as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a string (anything in quotes)

    19def test_passing_a_float():
20    a_float = 5.678
21    assert text(a_float) == f'I got: {a_float}'
22
23
24def test_passing_a_string():
25    assert text('hello') == 'I got: hi'
26
27
28# Exceptions seen

    the terminal is my friend, and shows AssertionError

    AssertionError: assert 'I got: hello'
                    == 'I got: hi'

GREEN: make it pass

I change my expectation to match reality

24def test_passing_a_string():
25    # assert text('hello') == 'I got: hi'
26    assert text('hello') == 'I got: hello'
27
28
29# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text('hello')
    text(the_input)
        the_input = 'hello'
        return f'I got: {the_input}'
        return  'I got:  hello     '

REFACTOR: make it better

  • I add a variable for 'hello'

    24def test_passing_a_string():
25    a_string = 'hello'
26    # assert text('hello') == 'I got: hi'
27    assert text('hello') == 'I got: hello'
28
29
30# Exceptions seen

  • I use the variable and an f-string to remove repetition of 'hello'

    24def test_passing_a_string():
25    a_string = 'hello'
26    # assert text('hello') == 'I got: hi'
27    # assert text('hello') == 'I got: hello'
28    assert text('hello') == f'I got: {a_string}'
29
30
31# Exceptions seen

    the test is still green.

  • I remove the commented lines

    24def test_passing_a_string():
25    a_string = 'hello'
26    assert text(a_string) == f'I got: {a_string}'
27
28
29# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am 'add test_passing_a_string'

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

I can pass a string as input to a function.

test_passing_a_tuple

Can I pass a tuple (anything in parentheses ( ) separated by a comma) as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a tuple

    24def test_passing_a_string():
25    a_string = 'hello'
26    assert text('hello') == f'I got: {a_string}'
27
28
29def test_passing_a_tuple():
30    assert text((0, 1, 2, 'n')) == 'I got: (0, 1, 2, n)'
31
32
33# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: (0, 1, 2, 'n')"
            == 'I got: (0, 1, 2, n)'

GREEN: make it pass

I change the tuple in my expectation to match reality

29def test_passing_a_tuple():
30    # assert text((0, 1, 2, 'n')) == 'I got: (0, 1, 2, n)'
31    assert text((0, 1, 2, 'n')) == "I got: (0, 1, 2, 'n')"
32
33
34# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text((0, 1, 2, 'n'))
    text(the_input)
        the_input = (0, 1, 2, 'n')
        return f'I got: {the_input    }'
        return  'I got:  (0, 1, 2, 'n')'

REFACTOR: make it better

  • I add a variable for (0, 1, 2, 'n')

    29def test_passing_a_tuple():
30    a_tuple = (0, 1, 2, 'n')
31    # assert text((0, 1, 2, 'n')) == 'I got: (0, 1, 2, n)'
32    assert text((0, 1, 2, 'n')) == "I got: (0, 1, 2, 'n')"
33
34
35# Exceptions seen

  • I use the variable and an f-string to remove repetition of (0, 1, 2, 'n')

    29def test_passing_a_tuple():
30    a_tuple = (0, 1, 2, 'n')
31    # assert text((0, 1, 2, 'n')) == 'I got: (0, 1, 2, n)'
32    # assert text((0, 1, 2, 'n')) == "I got: (0, 1, 2, 'n')"
33    assert text(a_tuple) == f'I got: {a_tuple}'
34
35
36# Exceptions seen

    the test is still green.

  • I remove the commented lines

    29def test_passing_a_tuple():
30    a_tuple = (0, 1, 2, 'n')
31    assert text(a_tuple) == f'I got: {a_tuple}'
32
33
34# Exceptions seen

  • I add a git commit message in the other terminal

    git commit --all --message \
'add test_passing_a_tuple'

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

I can pass a tuple as input to a function.

test_passing_a_list

Can I pass a list (anything in square brackets [ ]) from a test to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a list

    29def test_passing_a_tuple():
30    a_tuple = (0, 1, 2, 'n')
31    assert text(a_tuple) == f'I got: {a_tuple}'
32
33
34def test_passing_a_list():
35    assert text([0, 1, 2, 'n']) == 'I got: [0, 1, 2, "n"]'
36
37
38# Exceptions seen

    the terminal is my friend, and shows AssertionError

    assert "I got: [0, 1, 2, 'n']"
    == 'I got: [0, 1, 2, "n"]'

GREEN: make it pass

I change the list in my expectation to match reality

34def test_passing_a_list():
35    # assert text([0, 1, 2, 'n']) == 'I got: [0, 1, 2, "n"]'
36    assert text([0, 1, 2, 'n']) == "I got: [0, 1, 2, 'n']"
37
38
39# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text([0, 1, 2, 'n'])
    text(the_input)
        the_input = [0, 1, 2, 'n']
        return f'I got: {the_input    }'
        return  'I got:  [0, 1, 2, 'n']'

Python changed the double quotes (") in the list to a single quote (').

REFACTOR: make it better

  • I add a variable for [0, 1, 2, 'n']

    34def test_passing_a_list():
35    a_list = [0, 1, 2, 'n']
36    # assert text([0, 1, 2, 'n']) == 'I got: [0, 1, 2, "n"]'
37    assert text([0, 1, 2, 'n']) == "I got: [0, 1, 2, 'n']"
38
39
40# Exceptions seen

  • I use the variable and an f-string to remove repetition of [0, 1, 2, 'n']

    34def test_passing_a_list():
35    a_list = [0, 1, 2, 'n']
36    # assert text([0, 1, 2, 'n']) == 'I got: [0, 1, 2, "n"]'
37    # assert text([0, 1, 2, 'n']) == "I got: [0, 1, 2, 'n']"
38    assert text(a_list) == f'I got: {a_list}'
39
40
41# Exceptions seen

    the test is still green.

  • I remove the commented lines

    34def test_passing_a_list():
35    a_list = [0, 1, 2, 'n']
36    assert text(a_list) == f'I got: {a_list}'
37
38
39# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am 'add test_passing_a_list'

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

I can pass a list as input to a function.

test_passing_a_set

Can I pass a set (anything in curly braces { }, not key-value pairs) from a test to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a set

    34def test_passing_a_list():
35    a_list = [0, 1, 2, 'n']
36    assert text(a_list) == f'I got: {a_list}'
37
38
39def test_passing_a_set():
40    assert text({0, 1, 2, 'n'}) == 'I got: {0, 1, 2, "n"}'
41
42
43# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: {0, 1, 2, 'n'}"
            == 'I got: {0, 1, 2, "n"}'

GREEN: make it pass

  • I change the set in my expectation to match reality

    39def test_passing_a_set():
40    # assert text({0, 1, 2, 'n'}) == 'I got: {0, 1, 2, "n"}'
41    assert text({0, 1, 2, 'n'}) == "I got: {0, 1, 2, 'n'}"
42
43
44# Exceptions seen

  • I use ctrl/command+s (Windows & Linux/MacOS) to run the test a few times

    • if the result of text({0, 1, 2, 'n'}) is equal to "I got: {0, 1, 2, 'n'}" the test passes because Python uses the string representation of the object in the curly braces { }

      text({0, 1, 2, 'n'})
    text(the_input)
        the_input = {0, 1, 2, 'n'}
        return f'I got: {the_input    }'
        return  'I got:  {0, 1, 2, 'n'}'

    • if the result of text({0, 1, 2, 'n'}) is NOT equal to "I got: {0, 1, 2, 'n'}", the terminal shows AssertionError

      E       assert "I got: {0, 'n', 2, 1}"
            == "I got: {0, 1, 2, 'n'}"

    Python cannot guarantee the order of the things in the set and the order matters for the assertion that is comparing the strings because

    • these two are the same set

      {0, 'n', 2, 1} == {0, 1, 2, 'n'}

    • these two are not the same string

      "{0, 'n', 2, 1}" != "{0, 1, 2, 'n'}"

  • I add a variable for {0, 1, 2, 'n'}

    39def test_passing_a_set():
40    a_set = {0, 1, 2, 'n'}
41    # assert text({0, 1, 2, 'n'}) == 'I got: {0, 1, 2, "n"}'
42    assert text({0, 1, 2, 'n'}) == "I got: {0, 1, 2, 'n'}"
43
44
45# Exceptions seen

  • I use the variable and an f-string to remove repetition of {0, 1, 2, 'n'}

    39def test_passing_a_set():
40    a_set = {0, 1, 2, 'n'}
41    # assert text({0, 1, 2, 'n'}) == 'I got: {0, 1, 2, "n"}'
42    # assert text({0, 1, 2, 'n'}) == "I got: {0, 1, 2, 'n'}"
43    assert text(a_set) == f"I got: {a_set}"
44
45
46# Exceptions seen

    • I use ctrl/command+s (Windows & Linux/MacOS) to run the test a few times and the test stays green with no random failures because Python uses the string representation of the object in the curly braces { }.

    • It can guarantee the order when I use a variable and the f-string to refer to the same exact set.

REFACTOR: make it better

  • I remove the commented lines

    39def test_passing_a_set():
40    a_set = {0, 1, 2, 'n'}
41    assert text(a_set) == f"I got: {a_set}"
42
43
44# Exceptions seen

  • I add a git commit message in the other terminal

    git commit --all --message \
'add test_passing_a_set'

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

I can pass a set as input to a function.

test_passing_a_dictionary

Can I pass a dictionary (any key-value pairs in curly braces ‘{ }’ separated by commas) as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a test for a dictionary

    39def test_passing_a_set():
40    a_set = {0, 1, 2, 'n'}
41    assert text(a_set) == f"I got: {a_set}"
42
43
44def test_passing_a_dictionary():
45    reality = text({
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    })
49    my_expectation = (
50        "I got: "
51        "{key0: value0, keyN: [0, 1, 2, n]}"
52    )
53    assert reality == my_expectation
54
55
56# Exceptions seen

    the terminal is my friend, and shows AssertionError

    assert "I got: {'key..., 1, 2, 'n']}"
    == 'I got: {key0...[0, 1, 2, n]}'

    I want more detail in my error messages.

GREEN: make it pass

I change my_expectation to match reality

44def test_passing_a_dictionary():
45    reality = text({
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    })
49    my_expectation = (
50        "I got: "
51        # "{key0: value0, keyN: [0, 1, 2, n]}"
52        "{'key0': 'value0', 'keyN': [0, 1, 2, 'n']}"
53    )
54    assert reality == my_expectation
55
56
57# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text({'key0': 'value0', 'keyN': [0, 1, 2, 'n'],})
    text(the_input)
        the_input = {'key0': 'value0', 'keyN': [0, 1, 2, 'n']}
        return f'I got: {the_input}'
        return ("I got: {'key0': 'value0',"
                         'keyN': [0, 1, 2, 'n']}")

REFACTOR: make it better

  • I add a variable for {'key0': 'value0', 'keyN': [0, 1, 2, 'n'],}

    44def test_passing_a_dictionary():
45    a_dictionary = {
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    }
49    reality = text({
50        'key0': 'value0',
51        'keyN': [0, 1, 2, 'n'],
52    })
53    my_expectation = (
54        "I got: "
55        # "{key0: value0, keyN: [0, 1, 2, n]}"
56        "{'key0': 'value0', 'keyN': [0, 1, 2, 'n']}"
57    )
58    assert reality == my_expectation
59
60
61# Exceptions seen

  • I use the variable and an f-string to remove repetition of {'key0': 'value0', 'keyN': [0, 1, 2, 'n'],}

    44def test_passing_a_dictionary():
45    a_dictionary = {
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    }
49    # reality = text({
50    #     'key0': 'value0',
51    #     'keyN': [0, 1, 2, 'n'],
52    # })
53    # my_expectation = (
54    #     "I got: "
55    #     # "{key0: value0, keyN: [0, 1, 2, n]}"
56    #     "{'key0': 'value0', 'keyN': [0, 1, 2, 'n']}"
57    # )
58    reality = text(a_dictionary)
59    my_expectation = f'I got: {a_dictionary}'
60    assert reality == my_expectation
61
62
63# Exceptions seen

    the test is still green.

  • I remove the commented lines

    44def test_passing_a_dictionary():
45    a_dictionary = {
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    }
49    reality = text(a_dictionary)
50    my_expectation = f'I got: {a_dictionary}'
51    assert reality == my_expectation
52
53
54# Exceptions seen

  • I add a git commit message in the other terminal

    git commit -am \
'add test_passing_a_dictionary'

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

I can pass a dictionary as input to a function.

test_passing_a_class

Can I pass any object as input to a function?

RED: make it fail

  • I go back to the terminal where the tests are running

  • I add a failing test to see what happens when I pass a class from a test to the text function, in test_telephone.py

    44def test_passing_a_dictionary():
45    a_dictionary = {
46        'key0': 'value0',
47        'keyN': [0, 1, 2, 'n'],
48    }
49    reality = text(a_dictionary)
50    my_expectation = f'I got: {a_dictionary}'
51    assert reality == my_expectation
52
53
54def test_passing_a_class():
55    assert text(object) == 'I got: object'
56
57
58# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'object'>"
            == 'I got: object'

    object is the mother class that all Python classes come from because everything in Python is an object.

GREEN: make it pass

I change my expectation to match reality

54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57
58
59# Exceptions seen

the test passes because Python uses the string representation of the object in the curly braces { }

text(object)
    text(the_input)
        the_input = object
        return f'I got: {the_input       }'
        return  "I got:  <class 'object'> "

REFACTOR: make it better

  • I add an assertion for bool (the class for booleans)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    assert text(bool) == 'I got: bool'
58
59
60# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'bool'>"
            == 'I got: bool'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59
60
61# Exceptions seen

    the test passes.

  • I add an assertion for int (the class for whole numbers without decimals)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    assert text(int) == 'I got: int'
60
61
62# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'int'>"
            == 'I got: int'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61
62
63# Exceptions seen

    the test passes.

  • I add an assertion for float (the class for binary floating point decimal numbers)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    assert text(float) == 'I got: float'
62
63
64# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'float'>"
            == 'I got: float'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63
64
65# Exceptions seen

    the test passes.

  • I add an assertion for str (the class for anything in quotes)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    assert text(str) == 'I got: str'
64
65
66# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'str'>"
            == 'I got: str'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65
66
67# Exceptions seen

    the test passes.

  • I add an assertion for tuple (the class for anything in parentheses ( ) separated by a comma)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    assert text(tuple) == 'I got: tuple'
66
67
68# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'tuple'>"
            == 'I got: tuple'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67
68
69# Exceptions seen

    the test passes.

  • I add an assertion for list (the class for anything in square brackets ‘[ ]’)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    assert text(list) == 'I got: list'
68
69
70# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'list'>"
            == 'I got: list'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    # assert text(list) == 'I got: list'
68    assert text(list) == "I got: <class 'list'>"
69
70
71# Exceptions seen

    the test passes.

  • I add an assertion for set (the class anything in curly braces { }, not key-value pairs)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    # assert text(list) == 'I got: list'
68    assert text(list) == "I got: <class 'list'>"
69    assert text(set) == 'I got: set'
70
71
72# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'set'>"
            == 'I got: set'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    # assert text(list) == 'I got: list'
68    assert text(list) == "I got: <class 'list'>"
69    # assert text(set) == 'I got: set'
70    assert text(set) == "I got: <class 'set'>"
71
72
73# Exceptions seen

    the test passes.

  • I add an assertion for dict (the class for key-value pairs in curly braces ‘{ }’ separated by commas)

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    # assert text(list) == 'I got: list'
68    assert text(list) == "I got: <class 'list'>"
69    # assert text(set) == 'I got: set'
70    assert text(set) == "I got: <class 'set'>"
71    assert text(dict) == 'I got: dict'
72
73
74# Exceptions seen

    the terminal is my friend, and shows AssertionError

    E       assert "I got: <class 'dict'>"
            == 'I got: dict'

  • I change my expectation to match reality

    54def test_passing_a_class():
55    # assert text(object) == 'I got: object'
56    assert text(object) == "I got: <class 'object'>"
57    # assert text(bool) == 'I got: bool'
58    assert text(bool) == "I got: <class 'bool'>"
59    # assert text(int) == "I got: int"
60    assert text(int) == "I got: <class 'int'>"
61    # assert text(float) == 'I got: float'
62    assert text(float) == "I got: <class 'float'>"
63    # assert text(str) == 'I got: str'
64    assert text(str) == "I got: <class 'str'>"
65    # assert text(tuple) == 'I got: tuple'
66    assert text(tuple) == "I got: <class 'tuple'>"
67    # assert text(list) == 'I got: list'
68    assert text(list) == "I got: <class 'list'>"
69    # assert text(set) == 'I got: set'
70    assert text(set) == "I got: <class 'set'>"
71    # assert text(dict) == 'I got: dict'
72    assert text(dict) == "I got: <class 'dict'>"
73
74
75# Exceptions seen

    the test passes because Python uses the string representation of the object in the curly braces { }

    text(dict)
    text(the_input)
        the_input = dict
        return f'I got: {the_input     }'
        return  "I got:  <class 'dict'> "

  • I remove the commented lines

    54def test_passing_a_class():
55    assert text(object) == "I got: <class 'object'>"
56    assert text(bool) == "I got: <class 'bool'>"
57    assert text(int) == "I got: <class 'int'>"
58    assert text(float) == "I got: <class 'float'>"
59    assert text(str) == "I got: <class 'str'>"
60    assert text(tuple) == "I got: <class 'tuple'>"
61    assert text(list) == "I got: <class 'list'>"
62    assert text(set) == "I got: <class 'set'>"
63    assert text(dict) == "I got: <class 'dict'>"
64
65
66# Exceptions seen
67# AssertionError
68# NameError
69# TypeError

  • I add a git commit message in the other terminal

    git commit --all --message \
'add test_passing_a_class'

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

I can pass any object as input to a function.

close the project

  • I close test_telephone.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 telephone

    cd ..

    the terminal shows

    .../pumping_python

    I am back in the pumping_python directory.

review

Here are the tests I ran to see what happens when I pass objects from a test to a program and place them in an f-string which is one way to do string interpolation

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?

would you like to test making a person with f-strings?

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