Python Variables

A variable is a name used to store a value in a Python program. Python does not require a variable to be declared with a data type before assigning a value. The type is determined automatically from the value.

Creating a Variable

A variable is created using the assignment operator =.

name = "Rahul"
age = 20
marks = 85.5

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

Rahul
20
85.5

Dynamic Typing

Python is dynamically typed. A variable can refer to values of different types during program execution.

x = 10
print(x)

x = "Python"
print(x)

10
Python

Multiple Variable Assignment

Multiple variables can be assigned values in a single statement.

a, b, c = 10, 20, 30

print(a)
print(b)
print(c)

10
20
30

Same Value to Multiple Variables

x = y = z = 100

print(x, y, z)

100 100 100

Variable Naming Rules

• A variable name can contain letters, digits and underscore.
• A variable name cannot start with a digit.
• Spaces are not allowed in variable names.
• Special characters such as @, # and $ are not allowed.
• Python keywords cannot be used as variable names.
• Variable names are case-sensitive.

student_name = "Amit"
age2 = 21
_total = 500

Case-Sensitive Variables

Python treats uppercase and lowercase letters as different.

name = "Rahul"
Name = "Amit"

print(name)
print(Name)

Rahul
Amit

Variables and Data Types

Variables can store different types of values such as integers, floating-point numbers, strings and Boolean values.

age = 20
price = 99.50
name = "Python"
passed = True

print(type(age))
print(type(price))
print(type(name))
print(type(passed))

<class 'int'>
<class 'float'>
<class 'str'>
<class 'bool'>

Changing a Variable Value

The value of a variable can be changed by assigning a new value.

score = 50
print(score)

score = 80
print(score)

50
80

Variables in Expressions

Variables can be used in mathematical expressions and calculations.

a = 10
b = 20

sum_value = a + b
product = a * b

print("Sum =", sum_value)
print("Product =", product)

Sum = 30

Product = 200

Deleting a Variable

The del keyword can be used to remove a variable.

x = 10
print(x)

del x

Local and Global Variables

A variable created inside a function is generally called a local variable. A variable created outside a function is generally called a global variable.

x = 10

def display():
    y = 20
    print(x)
    print(y)

display()

10
20

Constants

Python does not provide a special keyword for constants. By convention, constant names are written in uppercase letters.

PI = 3.14159
MAX_MARKS = 100

print(PI)
print(MAX_MARKS)

Checking Variable Type

The type() function returns the data type of a variable.

value = 25

print(type(value))

<class 'int'>