Summary  
This chapter demonstrates how to use Python’s basic arithmetic operators (+, –, *, /) to perform addition, subtraction, multiplication, and division and display the results using printing.

General domain of usage  
Grocery cost calculation

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

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

import unittest
import io
import re
import importlib
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)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

class TestMathOperations(unittest.TestCase):

    def test_addition_printed_with_tolerance(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            importlib.reload(user_code)
        output = f.getvalue().strip().splitlines()
        try:
            value = float(output[0])
            expected = 5.42 + 4.39
            condition = abs(value - expected) <= 1e-2
        except Exception as e:
            _dynamic_test(self, False, "", f"Addition output parsing failed: {e}")
            return
        _dynamic_test(
            self,
            condition,
            f"Addition result correct within tolerance: {value}",
            f"Expected addition ~{expected:.2f}, got {value}"
        )

    def test_subtraction_printed_with_tolerance(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            importlib.reload(user_code)
        output = f.getvalue().strip().splitlines()
        try:
            # subtraction is second line
            value = float(output[1])
            expected = 12.30 - 5.50
            condition = abs(value - expected) <= 1e-2
        except Exception as e:
            _dynamic_test(self, False, "", f"Subtraction output parsing failed: {e}")
            return
        _dynamic_test(
            self,
            condition,
            f"Subtraction result correct within tolerance: {value}",
            f"Expected subtraction ~{expected:.2f}, got {value}"
        )

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

test_main.py

Python is a high-level, interpreted, general-purpose programming
language. Distinguished from languages such as HTML, CSS, and JavaScript, which are mainly
utilized in web development, Python boasts versatility across multiple domains, including
software development, data science, and back-end development. This course will guide you
through Python's fundamental concepts, equipping you with the skills to create your own
functions by the conclusion of the program.

Python

In this section, you will explore the fundamentals of Python, get acquainted
with your workspace, perform simple math operations, and display your findings.

In this section, you'll discover how to save items such as numbers and text
in computer memory and retrieve them by name. Additionally, you'll gain an introduction to text
manipulation in Python.

In this section, you'll explore the boolean data type and learn how it is used
to develop programs that react to certain conditions.

In this section, you will continue learning about data types and discover
how to organize various attributes in a single variable using lists, tuples, and dictionaries.

In this section, you'll learn how to create loops in Python — an essential skill
for iterating through lists, tuples, and dictionaries.

To conclude this introductory course, you will explore some built-in
functions and then begin to develop your own!

Simple Math: Add & Subtract

Requirements checklist

解答