Variables & Assignment

Variables are named references to values stored in memory. In Python, variables are dynamically typed — you don't declare a type, and a variable can point to different types throughout its life.

Basic Assignment

Assignment uses the = operator. The variable name goes on the left, the value on the right:

Python variables are references (pointers) to objects, not boxes containing values. When you do x = 42, Python creates an integer object with value 42 and makes x point to it.

Naming Conventions

Python follows PEP 8 naming conventions. Following them makes your code instantly readable to other Python developers:

Valid vs Invalid Names

Reserved keywords you cannot use as variable names: False, None, True, and, as, assert, async, await, break, class, continue, def, del, elif, else, except, finally, for, from, global, if, import, in, is, lambda, nonlocal, not, or, pass, raise, return, try, while, with, yield

Multiple Assignment

Python supports several forms of multiple assignment:

Augmented Assignment Operators

Augmented assignment modifies a variable in place (or rather, creates a new object and rebinds the name):

Constants by Convention

Python has no built-in constant mechanism — you can always reassign a variable. The community convention is to use UPPER_SNAKE_CASE for values that shouldn't change:

The Walrus Operator (:=)

Introduced in Python 3.8, the walrus operator (:=) assigns a value to a variable as part of an expression. This is useful when you want to both assign and test a value:

Common walrus operator patterns:

The walrus operator is intentionally different from = to avoid confusion. Use it when it genuinely reduces repetition — don't overuse it.

Variable Scope Preview

Variables have different scopes depending on where they're defined:

We'll explore scope in depth when we cover functions.

Deleting Variables

You can delete a variable with del:

del removes the name binding, not necessarily the object (which gets garbage collected when there are no more references to it).