Summary  
This chapter covers how to perform basic arithmetic operations—addition, subtraction, multiplication, and division—in Python using printing in code.

General domain of usage  
Grocery cost calculations

Python makes math operations simple and powerful. Use the following basic arithmetic operators:

- **Addition** (`+`)
- **Subtraction** (`-`)
- **Multiplication** (`*`)
- **Division** (`/`)

import unittest
import importlib
from io import StringIO
from contextlib import redirect_stdout


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_addition_operation_result_is_correct(self):
        # Test the first printed value: 5.42 + 4.39 should equal 9.81.
        import user_code
        output_capture = StringIO()
        with redirect_stdout(output_capture):
            importlib.reload(user_code)
        output = output_capture.getvalue().strip()
        lines = output.splitlines()

        if len(lines) < 1:
            _dynamic_test(self, False, "", "Missing addition result.")

        addition_result = lines[0].strip()
        expected_addition = str(5.42 + 4.39)
        condition = addition_result == expected_addition

        _dynamic_test(
            self,
            condition,
            "Addition result is correct.",
            f"Expected addition result to be '{expected_addition}' but got '{addition_result}'."
        )

    def test_subtraction_operation_result_is_correct(self):
        # Test the second printed value: 12.30 - 5.50 should equal 6.8.
        import user_code
        output_capture = StringIO()
        with redirect_stdout(output_capture):
            importlib.reload(user_code)
        output = output_capture.getvalue().strip()
        lines = output.splitlines()

        if len(lines) < 2:
            _dynamic_test(self, False, "", "Missing subtraction result.")

        subtraction_result = lines[1].strip()
        expected_subtraction = str(12.30 - 5.50)
        condition = subtraction_result == expected_subtraction

        _dynamic_test(
            self,
            condition,
            "Subtraction result is correct.",
            f"Expected subtraction result to be '{expected_subtraction}' but got '{subtraction_result}'."
        )

    def test_multiplication_operation_result_is_correct(self):
        # Test the third printed value: 7.32 * 0.2 should equal 1.464.
        import user_code
        output_capture = StringIO()
        with redirect_stdout(output_capture):
            importlib.reload(user_code)
        output = output_capture.getvalue().strip()
        lines = output.splitlines()

        if len(lines) < 3:
            _dynamic_test(self, False, "", "Missing multiplication result.")

        multiplication_result = lines[2].strip()
        expected_multiplication = str(7.32 * 0.2)
        condition = multiplication_result == expected_multiplication

        _dynamic_test(
            self,
            condition,
            "Multiplication result is correct.",
            f"Expected multiplication result to be '{expected_multiplication}' but got '{multiplication_result}'."
        )

    def test_division_operation_result_is_correct(self):
        # Test the fourth printed value: 8.30 / 20 should equal 0.415.
        import user_code
        output_capture = StringIO()
        with redirect_stdout(output_capture):
            importlib.reload(user_code)
        output = output_capture.getvalue().strip()
        lines = output.splitlines()

        if len(lines) < 4:
            _dynamic_test(self, False, "", "Missing division result.")

        division_result = lines[3].strip()
        expected_division = str(8.30 / 20)
        condition = division_result == expected_division

        _dynamic_test(
            self,
            condition,
            "Division result is correct.",
            f"Expected division result to be '{expected_division}' but got '{division_result}'."
        )


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


test_main.py

Gain a solid foundation in Python for data analysis. Learn to work with variables, data types, strings, conditional statements, loops, core data structures, and functions using examples relevant to analytical tasks.

Simple Arithmetics

Solution