Als de dataset rijen met null-waarden heeft, moeten we overwegen deze te verwijderen. In `pandas` kan dit worden bereikt met behulp van de `dropna()` methode.

import unittest
import importlib


def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)


class TestUserCode(unittest.TestCase):

    def test_length_before_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'length_before'),
            "The `length_before` variable is declared.",
            "Expected `length_before` to be declared."
        )

    def test_length_before_is_int(self):
        import user_code

        try:
            condition = isinstance(user_code.length_before, int)
            failure_message = f"Expected `length_before` to be `int`, but got `{type(user_code.length_before).__name__}`."
        except AttributeError:
            condition = False
            failure_message = "The `length_before` variable is not declared."

        _dynamic_test(
            self,
            condition,
            "The variable `length_before` is `int`.",
            failure_message
        )

    def test_length_before_is_correct(self):
        import user_code

        expected_value = 456

        try:
            condition = user_code.length_before == expected_value
            failure_message = f"Expected `length_before` to be `{expected_value}`, but got `{user_code.length_before}`."
        except AttributeError:
            condition = False
            failure_message = "The `length_before` variable is not declared."

        _dynamic_test(
            self,
            condition,
            f"`length_before` contains the correct value.",
            failure_message
        )

    def test_length_after_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'length_after'),
            "The `length_after` variable is declared.",
            "Expected `length_after` to be declared."
        )

    def test_length_after_is_int(self):
        import user_code

        try:
            condition = isinstance(user_code.length_after, int)
            failure_message = f"Expected `length_after` to be `int`, but got `{type(user_code.length_after).__name__}`."
        except AttributeError:
            condition = False
            failure_message = "The `length_after` variable is not declared."

        _dynamic_test(
            self,
            condition,
            "The variable `length_after` is `int`.",
            failure_message
        )

    def test_length_after_is_correct(self):
        import user_code

        expected_value = 450

        try:
            condition = user_code.length_after == expected_value
            failure_message = f"Expected `length_after` to be `{expected_value}`, but got `{user_code.length_after}`."
        except AttributeError:
            condition = False
            failure_message = "The `length_after` variable is not declared."

        _dynamic_test(
            self,
            condition,
            f"`length_after` contains the correct value.",
            failure_message
        )

    def test_wine_data_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'wine_data'),
            "The `wine_data` variable is declared.",
            "Expected `wine_data` to be declared."
        )

    def test_length_before_greater_than_length_after(self):
        import user_code

        try:
            condition = user_code.length_before > user_code.length_after
            failure_message = f"Expected `length_before` to be greater than `length_after`, but got `length_before`: {user_code.length_before}, `length_after`: {user_code.length_after}."
        except AttributeError:
            condition = False
            if not getattr(user_code, 'length_before', None):
                failure_message = "The `length_before` variable is not declared."
            else:
                failure_message = "The `length_after` variable is not declared."
        _dynamic_test(
            self,
            condition,
            f"`length_before` is greater than `length_after`.",
            failure_message
        )

    def test_wine_data_has_no_nulls(self):
        import user_code

        try:
            condition = not user_code.wine_data.isnull().values.any()
            failure_message = "Expected `wine_data` to have no null values, but null values are still present."
        except AttributeError:
            condition = False
            if not getattr(user_code, 'wine_data', None):
                failure_message = "The `wine_data` variable is not declared."
            else:
                failure_message = f"`wine_data` is not a `DataFrame`."
        _dynamic_test(
            self,
            condition,
            "`wine_data` has no null values after cleaning.",
            failure_message
        )


if __name__ == '__main__':
    unittest.main()

test_main.py

Pandas is een uiterst gebruiksvriendelijke bibliotheek voor data-analyse. Het is ook ontworpen om grote datasets te verwerken, met behulp van datastructuren zoals DataFrame en Series. Dit maakt het een onmisbaar hulpmiddel voor Data Science. In deze gids maak je kennis met een reeks statistische functies, waaronder hoe je correlaties, modi, mediaan, en maximale en minimale waarden binnen een dataset kunt vinden. Je leert ook hoe je omgaat met ontbrekende waarden en specifieke waarden kunt manipuleren, evenals hoe je ze kunt verwijderen.

In deze sectie verkennen we de basisprincipes van Series en DataFrame-structuren. Je leert ook over de verschillen tussen deze twee soorten structuren.

Gegevens kunnen in verschillende formaten worden verkregen, zoals CSV, JSON, SQL, HTML en meer. Met Pandas ben je niet beperkt tot één enkel formaat — je kunt werken met gegevens uit een veelheid aan bestandstypen. In dit hoofdstuk richten we ons specifiek op de CSV- en TXT-formaten.

Hier leer je hoe je ruwe gegevens kunt verwerken door overbodige informatie te verwijderen en null-waarden in een dataset te beheren.

Uitdaging: Nullwaarden Verwijderen

Oplossing