Variables

Overview

Variables in Python are names that refer to values stored in memory. Python is dynamically typed—you do not declare a type upfront. Assignment uses a single equals sign, and names should follow snake_case conventions for readability.

Syntax / Usage

# Basic assignment
name = "Ada"
age = 36
pi = 3.14159
is_active = True

# Multiple assignment
x, y, z = 1, 2, 3

# Reassignment changes the binding, not the original object
count = 10
count = count + 1  # now 11

# Constants by convention (not enforced)
MAX_RETRIES = 3

Variable names must start with a letter or underscore, cannot be Python keywords, and are case-sensitive (count ≠ Count).

Examples

Store user input and format a greeting:

first_name = input("First name: ")
last_name = "Lovelace"
greeting = f"Hello, {first_name} {last_name}!"
print(greeting)

Swap two values without a temporary variable:

a, b = 10, 20
a, b = b, a
print(a, b)  # 20 10

Common Mistakes

• Using = when you mean comparison (==) in conditionals
• Shadowing built-in names like list, str, or id
• Assuming assignment copies data—mutable objects share references
• Using reserved keywords (class, for, return) as variable names

See Also

python-data-types python-functions python-loops