Variables

Names that point at values

Beginner 10 min

In this lesson

Variables let you store a value and reuse it by name. You’ll learn how assignment works, how to name variables well, and the single most common beginner mix-up around the equals sign.

Explain it like I’m 5

A variable is a name tag you stick onto a value. Instead of repeating the value everywhere, you refer to it by its name — and you can move the tag onto a different value whenever you like.

Assignment: name on the left, value on the right

You create a variable with a single =: age = 36 means ‘let the name age refer to the value 36’. The right side is worked out first, then the name is attached to the result. Read = as ‘gets’ or ‘is set to’, not as ‘equals’.

Example 
first_name = "Ada"
birth_year = 1815
print(first_name, "was born in", birth_year)
Output 
Ada was born in 1815
Two variables, then used together.

Reassignment, and ‘names point at values’

You can point a name at a new value any time: age = 37. A helpful mental model is that variables are names that point at values, not boxes that contain them. x = 5 then y = x makes both names point at the same 5; later changing x doesn’t change y.

Example 
count = 0
count = count + 1
count = count + 1
print(count)
Output 
2
Reassigning a variable using its own current value.

Create a variable for a city, print a sentence with it, then reassign the variable to a different city and print again.

city = "Lagos"
print("I live in", city)

Naming rules and good names

Names may use letters, digits, and underscores, but can’t start with a digit or contain spaces. They’re case-sensitive: score and Score are different. By convention, use lowercase words joined by underscores (final_score). A good name describes the value’s meaning — price beats p.

Example 
score = 10
Score = 99
print(score, Score)
Output 
10 99
Case matters: score and Score are two different variables.

Assigning several variables at once

Python lets you set up several variables in a single line. x, y = 1, 2 assigns both at once. You can give several names the same starting value by chaining: a = b = c = 0. And you can swap two variables with no temporary helper: a, b = b, a.

These tricks all rely on Python pairing up the names on the left with the values on the right — the same ‘packing and unpacking’ idea behind tuples, which has its own lesson.

Example 
x, y = 1, 2
score = lives = 3
x, y = y, x

print(x, y)
print(score, lives)
Output 
2 1
3 3
Multiple assignment, shared values, and a clean swap.

Common mistake: Using a variable before assigning it

Why it happens:

Python runs top to bottom, so a name must be created on an earlier line than the line that uses it. Otherwise you get a NameError.

How to fix it:

Make sure the assignment (total = 0) appears above the first line that uses total.

total = 0
print(total)

After x = 5 and then x = 9, what does print(x) show?

Which checks whether a equals b (rather than assigning)?

Mini exercise (easy)

Create two variables, price (a number) and item (a string), then print a line like Apple costs 3.

Do it here. Finish the code below and press Run to try your answer right in the browser — no setup needed.

item = ""      # a string, e.g. "Apple"
price = 0      # a number
print(item, "costs", price)

What to learn next

You learned that a variable is a name pointing at a value rather than a box that holds it, how to assign and reassign, the naming rules and good style, and the classic = versus == trap. You applied it by storing an item and a price and printing them together.

You’ve been creating values of different kinds, text and numbers, without naming them as such. Python Data Types Overview gives you the vocabulary: str, int, float, bool, list, dict, and None, plus how to check any value’s type. When you’re ready, continue to the next lesson.