How do I create and use variables in Python?

· Category: Python Programming

Short answer

Python variables are created by assigning a value to a name using the = operator. Python uses dynamic typing, so you do not need to declare the type explicitly.

Steps

  1. Choose a valid variable name (must start with a letter or underscore, contain only letters, digits, and underscores, and cannot be a reserved keyword).
  2. Use the assignment operator = to bind a value to the name.
  3. Use the variable in expressions or pass it to functions.
# Creating variables
name = "Alice"
age = 30
is_student = False
pi = 3.14159

# Using variables
print(name)
greeting = f"Hello, {name}!"
print(greeting)

Tips

  • Follow PEP 8 naming conventions: use snake_case for variables and functions.
  • Variable names should be descriptive: user_count is better than uc.
  • You can reassign a variable to a value of a different type because Python is dynamically typed.
  • Use multiple assignment to swap values without a temporary variable: a, b = b, a.

Common issues

  • Using a variable before it is assigned raises a NameError.
  • Modifying a variable in one scope does not affect the same name in an outer scope unless you use the global or nonlocal keyword.
  • Mutable default arguments in functions can cause unexpected behavior because defaults are evaluated once at definition time.