Python Variables

Almost every program needs to remember something: a user's name, a score in a game, the total of a shopping cart. In Python, you remember things with variables. In this lesson, you'll learn how to create Python variables, change their values, and avoid the mistakes beginners make most often.

What is a variable in Python?

A variable is a name that points to a value. The value (like 25 or "Alice") is stored in your computer's memory, and the variable name is the label you use to reach it.

age = 25
name = "Alice"

print(name)
print(age)

Alice
25

Here, age and name are variables. The = sign means "store this value under this name". It does not mean "equals" like in math.

How to create a variable in Python

Creating a variable takes three parts: a name, the assignment operator =, and a value.

city = "London"      # text (a string)
temperature = 18.5   # a decimal number (a float)
is_raining = True    # True or False (a boolean)

Unlike languages such as Java or C, you don't declare a type first. Python looks at the value and works out the type by itself. This is called dynamic typing.

How variables work behind the scenes

When Python runs score = 10, it creates the value 10 in memory and attaches the name score to it. When you later write score = 15, Python doesn't erase the 10 and write 15 in its place. It creates a new value and moves the label.

Changing the value of a variable

Variables are called "variables" because their values can vary. Assign a new value at any time and the old one is replaced:

likes = 120
print(likes)

likes = 121          # someone liked the post
print(likes)

likes = likes + 1    # use the current value to calculate the new one
print(likes)

120
121
122

The line likes = likes + 1 looks strange in math, but in Python it simply means: take the current value of likes, add 1, and store the result back in likes.

A variable can hold any type of value

Because Python is dynamically typed, the same variable can even hold a different type later. You can check what type a variable holds with the built-in type() function:

data = 42
print(type(data))

data = "forty-two"
print(type(data))

<class 'int'>
<class 'str'>

Assigning multiple variables at once

Python lets you create several variables in one line. The values are matched to the names from left to right:

x, y, z = 4, 7, 9
print(x, y, z)

first_name, last_name = "Ada", "Lovelace"
print(first_name, last_name)

4 7 9
Ada Lovelace

You can also give the same value to several variables:

wins = losses = draws = 0
print(wins, losses, draws)

0 0 0

Swapping two variables

In many languages, swapping two values needs a third "temporary" variable. Python does it in one line:

left = "coffee"
right = "tea"

left, right = right, left

print(left)
print(right)

tea
coffee

Constants: values that should not change

Some values should stay the same for the whole program, like the number of minutes in an hour or a tax rate. Python has no special keyword for constants. Instead, programmers write the name in ALL CAPS as a signal to everyone reading the code: "don't change this".

SALES_TAX = 0.08
price = 50

total = price + price * SALES_TAX
print(total)

54.0

Deleting a variable

You rarely need to, but you can remove a variable with the del keyword. After that, using the name causes an error:

password = "s3cret"
del password
print(password)

NameError: name 'password' is not defined

Real-world example: a shopping cart total

Here's how variables work together in a small, realistic program. Each value gets a clear name, and the final line uses those names to build a message.

item = "Wireless headphones"
price = 59.99
quantity = 2
shipping = 4.99

subtotal = price * quantity
total = subtotal + shipping

print("Item:", item)
print("Subtotal:", subtotal)
print("Total to pay:", total)

Item: Wireless headphones
Subtotal: 119.98
Total to pay: 124.97

If the price changes, you only update one line (price = 49.99) and every calculation that uses it updates too. That's the real power of variables.

Common mistakes with variables

1. Using a variable before creating it

print(total)
total = 100

NameError: name 'total' is not defined

Python runs code from top to bottom, so a variable must be assigned before the line that uses it.

2. Spelling the name differently

Python is case-sensitive: Score, score and SCORE are three different variables.

score = 10
print(Score)

NameError: name 'Score' is not defined. Did you mean: 'score'?

3. Putting the name on the right side

25 = age

SyntaxError: cannot assign to literal here. Maybe you meant '==' instead of '='?

The name always goes on the left of =, and the value on the right.

4. Forgetting quotes around text

country = Canada

NameError: name 'Canada' is not defined

Without quotes, Python thinks Canada is another variable. Text must be inside quotes: country = "Canada".

Practice exercise

name = "Sam"
monday = 20
tuesday = 25

total = monday + tuesday
print(name, "did", total, "push-ups this week.")

Sam did 45 push-ups this week.

What's next?

Now you know how to create and use variables. Next, learn the rules for naming variables in Python, so your code is valid and easy to read.