Variables in Python

In this Python tutorial, we will learn what variables are, how to declare a variable, how to assign values to variables, and how to read the values from variables.

Python Variables

In Python, a variable is a name that refers to a value. You use variables to store values such as numbers, text, lists, and results of calculations so that you can use them later in a program.

It is common to say that variables are containers for values. In Python, a more precise way to think about them is this: a variable name is bound to an object in memory. When you assign a new value to the same name, the name can refer to a different object.

Creating a Python Variable by Assignment

Assignment Operator = can be used to assign values to variables. Variable must be the left operand and the value assigned to it must be right operand. An example to assign a variable a with value 100 is given in the following.

a = 100

There is no explicit declaration required for a variable in Python, unlike in many other programming languages. When a variable is used in the python code, python interpreter automatically interprets the data type from the value assigned to the variable.

For example, the following statements create three variables. Python decides the type from the assigned value.

count = 10
price = 49.95
message = "Hello Python"

Python Variables Do Not Need a Declared Data Type

Python is dynamically typed. This means the type is associated with the value at runtime, not permanently fixed to the variable name. The same variable name can refer to an integer first and a string later.

x = 25
print(type(x))

x = "Python"
print(type(x))

Output

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

This flexibility is useful, but it also means that you should choose clear variable names and avoid reusing the same name for unrelated values in the same part of a program.

Reading Values from Python Variables

To read the value stored in a variable, the variable has to be given on the righthand side of the assignment operator, or in an expression, etc.

In the following example, we take two variables a and b and assign them with integer values. We try to add the values stored in these two variables. We read the values from variables by including them in an expression, which in this case is a + b.

While Python interprets this code, a and b are substituted with the values stored in them.

Example.py

a = 10
b = 20
total = a + b
print(total)

Output

30

You can use variables in calculations, function calls, comparisons, loops, and conditional statements. A variable must be assigned a value before you read it. Otherwise, Python raises a NameError.

total = marks + 10
print(total)

Output

NameError: name 'marks' is not defined

Python Variable Naming Rules

A Python variable name must follow a few rules. A valid variable name can contain letters, digits, and underscores, but it cannot start with a digit. Variable names are case-sensitive, so total, Total, and TOTAL are three different names.

• Use names such as student_name, total_marks, and is_valid for readable Python code.
• Do not use spaces or special characters such as @, -, or # in variable names.
• Do not use Python keywords such as for, if, class, or return as variable names.
• Prefer lowercase words separated by underscores for normal variable names.

student_name = "Arun"
total_marks = 92
is_passed = True

The following names are not valid Python variable names.

2total = 50
student-name = "Arun"
class = "Python"

Common Data Types Stored in Python Variables

A Python variable can refer to values of many data types. The most common beginner-level examples are integers, floating-point numbers, strings, booleans, lists, tuples, dictionaries, and sets.

Value assigned to variable	Python data type	Example
Whole number	int	age = 18
Decimal number	float	price = 99.5
Text	str	name = "Ravi"
True or false value	bool	is_active = True
Ordered, changeable collection	list	marks = [80, 85, 90]
Key-value collection	dict	student = {"name": "Ravi"}

You can check the type of a value using the built-in type() function.

name = "Ravi"
age = 18
marks = [80, 85, 90]

print(type(name))
print(type(age))
print(type(marks))

Output

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

Assigning Multiple Python Variables in a Single Line

In Python, we can assign multiple variables a value in a single statement.

In the following program, we take variables for months and assign values of 31 for months with 31 days, 30 for months with 30 days, and 28 for feb. We assign all the months with 31 days in a single statement. Similarly for months with 30 days.

Example.py

jan = mar = may = jul = aug = oct = dec = 31
apr = jun = sep = nov = 30
feb = 28
total = jan + feb + mar + apr + may + jun + jul + aug + sep + oct + nov + dec
print(total)

Output

365

You can also assign different values to different variables in one statement. The number of variables on the left should match the number of values on the right.

name, age, city = "Ravi", 18, "Hyderabad"

print(name)
print(age)
print(city)

Output

Ravi
18
Hyderabad

Updating the Value of a Python Variable

After a variable is created, you can update it by assigning a new value to the same name. The old binding is replaced by the new one.

score = 50
print(score)

score = score + 10
print(score)

Output

50
60

The expression score = score + 10 reads the current value of score, adds 10, and assigns the result back to score.

Variables Referring to the Same Python Object

More than one variable name can refer to the same object. This matters especially when the object is mutable, such as a list or dictionary.

numbers = [10, 20, 30]
same_numbers = numbers

same_numbers.append(40)

print(numbers)
print(same_numbers)

Output

[10, 20, 30, 40]
[10, 20, 30, 40]

Both names refer to the same list object in this example. When the list is changed through same_numbers, the change is visible through numbers too.

Constants in Python Programs

Python does not have a built-in constant keyword for normal variables. By convention, programmers write constant-like names in uppercase letters to show that the value should not be changed.

PI = 3.14159
MAX_USERS = 100
DEFAULT_LANGUAGE = "English"

This is a naming convention, not a strict rule enforced by Python. A program can still assign a new value to PI, but it should not do so if the name is being used as a constant.

Common Mistakes with Python Variables

• Using a variable before assigning it: assign a value before reading the variable.
• Mixing uppercase and lowercase names: marks and Marks are different variables.
• Choosing unclear names: prefer total_price over names such as x when the meaning is important.
• Using invalid characters: use underscores instead of hyphens or spaces.
• Assuming the variable has a fixed type: the name can be rebound to a value of another type.

Quick Practice on Python Variables

Try to predict the output before looking at the answer.

item = "Book"
price = 120
quantity = 3

total_price = price * quantity

print(item)
print(total_price)

Output

Book
360

Python Variables Editorial QA Checklist

• Does the tutorial explain that Python variables are names bound to values, not fixed typed containers?
• Are all Python variable examples runnable without missing definitions, except the intentional NameError example?
• Are variable naming rules shown with both valid and invalid examples?
• Are output blocks clearly separated from Python code blocks?
• Does the explanation distinguish assignment, reading a value, updating a value, and multiple assignment?

Frequently Asked Questions on Python Variables

Python Variables Summary

In this Python Tutorial, we learned about variables in Python: how assignment creates a variable name, how to read and update values, how multiple assignment works, how Python handles data types dynamically, and which naming rules help keep Python code readable.