Summary  
This chapter covers performing simple math operations in code using the +, - , * , and / operators for addition, subtraction, multiplication, and division.  

General domain of usage  
Calculating costs in retail pricing.

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

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

import unittest
import re
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  # The user solution file is named user_code.py
        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)  # Expected result: 9.81
        condition = addition_result == expected_addition

        _dynamic_test(
            self,
            condition,
            "Addition result is correct.",
            f"Expected addition result to be '{expected_addition}' but got '{lines[0].strip()}'."
        )

    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)  # Expected result: 6.8
        condition = subtraction_result == expected_subtraction

        _dynamic_test(
            self,
            condition,
            "Subtraction result is correct.",
            f"Expected subtraction result to be '{expected_subtraction}' but got '{lines[1].strip()}'."
        )

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


Simple Math: Add & Subtract

Solution