Numbers and Basic Operators

🎯 Learning Objective

After this lesson, you will be able to:

• Work confidently with Python integers and floating-point values.
• Use arithmetic operators with readable intermediate results.
• Distinguish /, //, and % in practical calculations.
• Apply precedence, parentheses, augmented assignment, and exponentiation correctly.

Short Explanation

Python uses integers for whole numbers and floats for decimal values. The familiar operators +, -, *, and / handle basic arithmetic. Normal division with / returns a float, even when the result is mathematically whole.

// returns the floor-divided result, while % returns the remainder. They are commonly used together for pagination, batching, time conversion, and fixed-size groups.

** means exponentiation. Augmented assignments such as += and -= update an existing value without repeating its name.

Python follows operator precedence: powers first, then multiplication and division, then addition and subtraction. Use parentheses when they make the business rule clearer or change the required order.

💡 Tip: Store meaningful intermediate values such as subtotal, remaining_seconds, or completion_rate instead of hiding an entire calculation inside one print statement.

Clean Code Examples

1. Combine basic operations

Multiplication happens before addition and subtraction.

base_fee = 18
extra_users = 4
credit = 5

total = base_fee + extra_users * 3 - credit
print(total)

Output:

25

2. Compare division, floor division, and remainder

The same values answer three different questions.

records = 47
batch_size = 10

print(records / batch_size)
print(records // batch_size)
print(records % batch_size)

Output:

4.7
4
7

3. Update a running value

Augmented assignment changes the current value in place.

processed_rows = 120
processed_rows += 35
processed_rows -= 5

print(processed_rows)

Output:

150

4. Use exponentiation

** raises the left value to the power on the right.

side_length = 6
square_area = side_length ** 2

print(square_area)

Output:

36

⚠️ Common Mistakes

1. Do not expect / to return an integer.
2. Do not confuse the full-group result from // with the leftover result from %.
3. Do not use ^ for exponentiation; in Python it has a different meaning.
4. Do not rely on remembered precedence when parentheses would make the rule clearer.