Python Variables

What Is A Variable?

A variable is a name that refers to a value in a program. When you write Python code, you often need to store information so you can use it later. That information may be a number, a piece of text, a true-or-false value, or a larger structure such as a list.

In beginner terms, think of a variable as a useful label. The label helps you remember what a value means. Instead of writing the number 85 everywhere, you can write score = 85. Now the name score makes your code easier to read.

score = 85
name = "Asha"
is_passed = True

In these examples, score, name, and is_passed are variable names. The values are 85, "Asha", and True.

Basic Assignment Syntax

Python uses the equals sign = for assignment.

variable_name = value

The right side is evaluated first. Then the result is stored using the name on the left side.

price = 50
quantity = 3
total = price * quantity

print(total)

This prints:

150

Python first finds the values of price and quantity, multiplies them, and stores the result in total.

Variables Can Change

A variable can receive a new value later in the program.

score = 5
score = 8

print(score)

This prints:

8

The second assignment replaces the value that the name score refers to. Python does not keep both values inside the same variable name.

You can also update a variable by using its old value:

marks = 70
marks = marks + 5

print(marks)

This prints:

75

Python evaluates marks + 5 first. Since marks is currently 70, the expression becomes 75. Then the name marks is updated to refer to 75.

Naming Rules

Python variable names must follow a few rules:

• A name can contain letters, digits, and underscores.
• A name cannot start with a digit.
• A name cannot contain spaces.
• A name cannot use Python keywords such as for, if, class, or while.
• Variable names are case-sensitive.

Valid examples:

student_name = "Riya"
marks2 = 91
total_score = 450

Invalid examples:

2marks = 91
student name = "Riya"
class = "Python"
total-score = 450

The name total-score is invalid because Python treats the hyphen as a minus operator. Use total_score instead.

Recommended Naming Style

Python style usually uses snake_case for normal variable names. That means lowercase words separated by underscores.

first_name = "Aman"
total_marks = 478
average_score = 79.6

Names like firstName or TotalMarks may work, but they are not the usual style for normal Python variables. A clear name is better than a very short or confusing one.

Compare these:

x = 80
y = 90
z = x + y

This works, but it is not very meaningful. The next version is easier to understand:

math_marks = 80
science_marks = 90
total_marks = math_marks + science_marks

Readable names become more important as programs become longer.

Printing Variables And Text

There is an important difference between printing a variable and printing text.

name = "Python"

print(name)
print("name")

Output:

Python
name

print(name) prints the value stored in the variable. print("name") prints the exact text inside quotes.

This mistake is common for beginners. If you expect the variable value, do not put the variable name inside quotes.

Multiple Variables

Python can assign values to more than one variable in one line:

x, y = 10, 20

Now x stores 10 and y stores 20.

This is also useful for swapping values:

a = 5
b = 9

a, b = b, a

print(a)
print(b)

Output:

9
5

Python evaluates the right side first, then assigns the values to the names on the left.

Common Mistakes

One common mistake is using == when you mean assignment.

score == 10

This does not assign 10 to score. The == operator compares two values. To assign, use:

score = 10

Another common mistake is using a variable before assigning it.

print(total)

If total has not been assigned yet, Python raises a NameError because it does not know what value the name should refer to.

A third mistake is using unclear names:

a = 1200
b = 18
c = a * b

The code may run, but another learner cannot easily understand what the values mean. Better names make the purpose clear:

monthly_fee = 1200
months = 18
total_fee = monthly_fee * months

Quick Summary

• A variable is a name that refers to a value.
• Use = to assign a value.
• Python evaluates the right side before assigning to the left side.
• Variable names should be clear and usually use snake_case.
• Do not put a variable name in quotes when you want its stored value.
• Use == for comparison, not assignment.
• A variable must be assigned before you use it.

Practice Quiz

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