functions 3: use class attributes

In AssertionError 2: use class attributes I used class attributes to remove repetition from the assertion_error project. The classes chapter teaches the setUp method to ensure each test method starts with fresh values. In some cases the values I need are the same for every test. In this case, I do not need the setUp method because the class attributes are the same for every test and I do not need anything to run before each test. I want to do the same thing in the functions project.

preview

I have these tests by the end of the chapter

continue the project

I change directory to the functions folder
```
cd functions
```
the terminal shows I am in the functions folder
```
.../pumping_python/functions
```

I use pytest-watcher to run the tests

uv run pytest-watcher . --now

the terminal is my friend, and shows

rootdir: .../pumping_python/functions
configfile: pyproject.toml
collected 12 items

tests/test_functions.py ............                  [100%]

=================== 12 passed in X.YZs =====================

I hold ctrl on the keyboard, then click on tests/test_functions.py to open it

I add class attributes

class TestFunctions(unittest.TestCase):

    first = 'first'
    last = 'last'

    def test_why_use_a_function(self):

I use the class attributes to remove repetition of 'first' and 'last' from test_positional_arguments

    def test_positional_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.positional_arguments(
            # first, last,
            self.first, self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

the test is still green.

I use the class attributes to remove repetition of 'first' and 'last' from test_keyword_arguments

    def test_keyword_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.w_keyword_arguments(
            # first_input=first, last_input=last,
            first_input=self.first,
            last_input=self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last_input=last, first_input=first,
            last_input=self.last,
            first_input=self.first,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

still green.

I use the class attributes to remove 'first' and 'last' from test_args_and_kwargs

    def test_args_and_kwargs(self):
        # first, last = 'first', 'last'
        reality = (
            src.functions.args_and_kwargs(
                # first, last_input=last,
                self.first, last_input=self.last,
            )
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

    def test_optional_arguments(self):

green.

I remove the commented lines from test_args_and_kwargs

    def test_args_and_kwargs(self):
        reality = (
            src.functions.args_and_kwargs(
                self.first, last_input=self.last,
            )
        )
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

    def test_optional_arguments(self):

I add a class attribute

class TestFunctions(unittest.TestCase):

    first = 'first'
    last = 'last'
    a_tuple = (0, 1, 2, 'n')

    def test_why_use_a_function(self):

I use the new class attribute to remove repetition of (0, 1, 2, 'n') from test_positional_arguments

    def test_positional_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.positional_arguments(
            # first, last,
            self.first, self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        first_number, second_number = 0, 1
        reality = src.functions.positional_arguments(
            first_number, second_number,
        )
        my_expectation = (first_number, second_number)
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            # a_tuple, a_list,
            self.a_tuple, a_list,
        )
        # my_expectation = (a_tuple, a_list)
        my_expectation = (self.a_tuple, a_list)
        self.assertEqual(reality, my_expectation)

    def test_keyword_arguments(self):

still green.

I use the new class attribute to remove repetition of (0, 1, 2, 'n') from test_keyword_arguments

    def test_keyword_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.w_keyword_arguments(
            # first_input=first, last_input=last,
            first_input=self.first,
            last_input=self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last_input=last, first_input=first,
            last_input=self.last,
            first_input=self.first,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        zero, one = 0, 1
        reality = src.functions.w_keyword_arguments(
            last_input=zero, first_input=one,
        )
        my_expectation = (one, zero)
        self.assertEqual(reality, my_expectation)

        a_set = {0, 1, 2, 'n'}
        a_dictionary = {'key': 'value'}
        reality = src.functions.w_keyword_arguments(
            first_input=a_set,
            last_input=a_dictionary,
        )
        my_expectation = (a_set, a_dictionary)
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            first_input=a_list,
            # last_input=a_tuple,
            last_input=self.a_tuple,
        )
        # my_expectation = (a_list, a_tuple)
        my_expectation = (a_list, self.a_tuple)
        self.assertEqual(reality, my_expectation)

    def test_args_and_kwargs(self):

the test is still green.

I add a class attribute

class TestFunctions(unittest.TestCase):

    first = 'first'
    last = 'last'
    a_tuple = (0, 1, 2, 'n')
    a_list = [0, 1, 2, 'n']

    def test_why_use_a_function(self):

I use the new class attribute to remove repetition of [0, 1, 2, 'n'] from test_positional_arguments

    def test_positional_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.positional_arguments(
            # first, last,
            self.first, self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        first_number, second_number = 0, 1
        reality = src.functions.positional_arguments(
            first_number, second_number,
        )
        my_expectation = (first_number, second_number)
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        # a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            # a_tuple, a_list,
            # self.a_tuple, a_list,
            self.a_tuple, self.a_list,
        )
        # my_expectation = (a_tuple, a_list)
        # my_expectation = (self.a_tuple, a_list)
        my_expectation = (self.a_tuple, self.a_list)
        self.assertEqual(reality, my_expectation)

    def test_keyword_arguments(self):

still green.

I use the new class attribute to remove repetition of [0, 1, 2, 'n'] from test_keyword_arguments

    def test_keyword_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.w_keyword_arguments(
            # first_input=first, last_input=last,
            first_input=self.first,
            last_input=self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last_input=last, first_input=first,
            last_input=self.last,
            first_input=self.first,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        zero, one = 0, 1
        reality = src.functions.w_keyword_arguments(
            last_input=zero, first_input=one,
        )
        my_expectation = (one, zero)
        self.assertEqual(reality, my_expectation)

        a_set = {0, 1, 2, 'n'}
        a_dictionary = {'key': 'value'}
        reality = src.functions.w_keyword_arguments(
            first_input=a_set,
            last_input=a_dictionary,
        )
        my_expectation = (a_set, a_dictionary)
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        # a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            # first_input=a_list,
            # last_input=a_tuple,
            first_input=self.a_list,
            last_input=self.a_tuple,
        )
        # my_expectation = (a_list, a_tuple)
        # my_expectation = (a_list, self.a_tuple)
        my_expectation = (self.a_list, self.a_tuple)
        self.assertEqual(reality, my_expectation)

    def test_args_and_kwargs(self):

green.

I add class attribute

class TestFunctions(unittest.TestCase):

    first = 'first'
    last = 'last'
    a_tuple = (0, 1, 2, 'n')
    a_list = [0, 1, 2, 'n']
    first_number = 0
    second_number = 1

    def test_why_use_a_function(self):

I use the new class attributes to remove repetition of 0 and 1 from test_positional_arguments

    def test_positional_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.positional_arguments(
            # first, last,
            self.first, self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        # first_number, second_number = 0, 1
        reality = src.functions.positional_arguments(
            # first_number, second_number,
            self.first_number, self.second_number,
        )
        # my_expectation = (first_number, second_number)
        my_expectation = (
            self.first_number, self.second_number
        )
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        # a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            # a_tuple, a_list,
            # self.a_tuple, a_list,
            self.a_tuple, self.a_list,
        )
        # my_expectation = (a_tuple, a_list)
        # my_expectation = (self.a_tuple, a_list)
        my_expectation = (self.a_tuple, self.a_list)
        self.assertEqual(reality, my_expectation)

    def test_keyword_arguments(self):

still green.

I remove the commented lines from test_positional_arguments

    def test_positional_arguments(self):
        reality = src.functions.positional_arguments(
            self.first, self.last,
        )
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            self.last, self.first,
        )
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            self.first_number, self.second_number,
        )
        my_expectation = (
            self.first_number, self.second_number
        )
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            self.a_tuple, self.a_list,
        )
        my_expectation = (self.a_tuple, self.a_list)
        self.assertEqual(reality, my_expectation)

    def test_keyword_arguments(self):

I use the new class attributes to remove repetition of 0 and 1 from test_keyword_arguments

    def test_keyword_arguments(self):
        # first, last = 'first', 'last'

        reality = src.functions.w_keyword_arguments(
            # first_input=first, last_input=last,
            first_input=self.first,
            last_input=self.last,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last_input=last, first_input=first,
            last_input=self.last,
            first_input=self.first,
        )
        # my_expectation = (first, last)
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            # last, first,
            self.last, self.first,
        )
        # my_expectation = (last, first)
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        # zero, one = 0, 1
        reality = src.functions.w_keyword_arguments(
            # last_input=zero, first_input=one,
            last_input=self.first_number,
            first_input=self.second_number,
        )
        # my_expectation = (one, zero)
        my_expectation = (
            self.second_number, self.first_number
        )
        self.assertEqual(reality, my_expectation)

        a_set = {0, 1, 2, 'n'}
        a_dictionary = {'key': 'value'}
        reality = src.functions.w_keyword_arguments(
            first_input=a_set,
            last_input=a_dictionary,
        )
        my_expectation = (a_set, a_dictionary)
        self.assertEqual(reality, my_expectation)

        # a_tuple = (0, 1, 2, 'n')
        # a_list = [0, 1, 2, 'n']
        reality = src.functions.positional_arguments(
            # first_input=a_list,
            # last_input=a_tuple,
            first_input=self.a_list,
            last_input=self.a_tuple,
        )
        # my_expectation = (a_list, a_tuple)
        # my_expectation = (a_list, self.a_tuple)
        my_expectation = (self.a_list, self.a_tuple)
        self.assertEqual(reality, my_expectation)

    def test_args_and_kwargs(self):

I remove the commented lines from test_keyword_arguments

    def test_keyword_arguments(self):
        reality = src.functions.w_keyword_arguments(
            first_input=self.first,
            last_input=self.last,
        )
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            last_input=self.last,
            first_input=self.first,
        )
        my_expectation = (self.first, self.last)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            self.last, self.first,
        )
        my_expectation = (self.last, self.first)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.w_keyword_arguments(
            last_input=self.first_number,
            first_input=self.second_number,
        )
        my_expectation = (
            self.second_number, self.first_number
        )
        self.assertEqual(reality, my_expectation)

        a_set = {0, 1, 2, 'n'}
        a_dictionary = {'key': 'value'}
        reality = src.functions.w_keyword_arguments(
            first_input=a_set,
            last_input=a_dictionary,
        )
        my_expectation = (a_set, a_dictionary)
        self.assertEqual(reality, my_expectation)

        reality = src.functions.positional_arguments(
            first_input=self.a_list,
            last_input=self.a_tuple,
        )
        my_expectation = (self.a_list, self.a_tuple)
        self.assertEqual(reality, my_expectation)

    def test_args_and_kwargs(self):

I add a git commit message

git commit -am 'extract class attributes'

I can use class attributes to remove repetition

close the project

I close test_functions.py and functions.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.tests. The terminal goes back to the command line.
I change directory to the parent of functions
```
cd ..
```
the terminal shows
```
.../pumping_python
```
I am back in the pumping_python directory.

review

In AssertionError 2: use class attributes I used class attributes to remove repetition. The classes chapter shows the setUp method to make new values before every test, for example when I want random values for each test.

In some cases the values I need are the same for every test, which means I do not need the setUp method because the class attributes are the same for every test and I do not need anything to run before each test.

I can place the constants directly under the TestFunctions class:

first = 'first'
last = 'last'
a_tuple = (0, 1, 2, 'n')
a_list = [0, 1, 2, 'n']
first_number = 0
second_number = 1

then test_positional_arguments, test_keyword_arguments and test_args_and_kwargs use self.first and so on, instead repeated values.

I can use class attributes for things that repeat (when they are constants), which allows methods of the same class to use them without the setUp method.

code from the chapter

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

what is next?

Here is another reminder, you know

Would you like to test AttributeError?

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