Operators and Expressions

Arithmetic, comparison, logical, and assignment operators in Python.

Overview

Operators are symbols that perform operations on values. Python provides a comprehensive set of operators organized into several categories: **Arithmetic operators** perform math: +, -, *, /, // (floor division), % (modulo), ** (exponentiation). **Comparison operators** compare two values and return True or False: ==, !=, <, >, <=, >=. A common beginner mistake is using = (assignment) where == (comparison) is needed. **Logical operators** combine boolean expressions: and, or, not. Python evaluates them with short-circuit logic it stops as soon as the result is determined. **Assignment operators** are shortcuts for common patterns: +=, -=, *=, /=, //=, **=, %= all modify a variable in place. An **expression** is anything that produces a value from a simple literal like 42 to complex combined operations like (a + b) * c // 2. Python evaluates expressions following standard mathematical precedence (PEMDAS), which you can always override with parentheses.

Key Points

•/ always returns float in Python 3; use // for integer (floor) division
•% is the modulo (remainder) operator: 10 % 3 == 1
•Comparison operators return True or False; == checks equality, = assigns
•and/or/not are the logical operators (not &&/||/! as in C-style languages)
•and and or short-circuit: `a and b` only evaluates b if a is truthy
•Augmented assignment: `x += 5` is equivalent to `x = x + 5`
•Python respects standard operator precedence; use parentheses to clarify

Examples

Arithmetic operators

print(10 + 3)    # 13 addition
print(10 - 3)    # 7 subtraction
print(10 * 3)    # 30 multiplication
print(10 / 3)    # 3.3333... true division (always float)
print(10 // 3)   # 3 floor division
print(10 % 3)    # 1 modulo (remainder)
print(10 ** 3)   # 1000 exponentiation

Comparison and logical operators

x = 5
print(x == 5)        # True
print(x != 5)        # False
print(x > 3)         # True
print(x >= 10)       # False

# Logical operators
print(x > 3 and x < 10)   # True
print(x > 10 or x == 5)   # True
print(not x == 5)          # False

# Python allows chained comparisons
print(1 < x < 10)         # True very Pythonic!

Augmented assignment operators

score = 0
score += 10    # score = score + 10 → 10
score *= 2     # score = score * 2  → 20
score -= 5     # score = score - 5  → 15
print(score)   # 15

Common Mistakes

Using = instead of == in a condition: `if x = 5:` is a SyntaxError; use `if x == 5:`
Unexpected float result from /: if you need an integer, use // deliberately
Confusing and/or with bitwise &/| they are different operators with different behaviour

Note

Use Python's interactive REPL to test operator precedence: try `2 + 3 * 4` (14) vs `(2 + 3) * 4` (20) to see how Python evaluates expressions.

Operators and Expressions

Overview

Key Points

Examples

Common Mistakes

Note

Exercises

Knowledge Check

What is the result of `15 % 4` in Python?