Python Variables

A variable is a name used to store a value in a Python program. Python variables are created when a value is assigned to a name. No separate declaration of the variable type is required.

Creating a Variable

The assignment operator = is used to assign a value to a variable.

name = "Rahul"
age = 20
marks = 85.5

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

Rahul
20
85.5

Dynamic Typing in Python

Python is a dynamically typed language. A variable does not need a fixed data type. Its type is determined automatically from the value assigned to it.

x = 10
print(x)

x = "Python"
print(x)

10
Python

Multiple Variable Assignment

Python allows multiple variables to be assigned values in a single statement.

a, b, c = 10, 20, 30

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

10
20
30

Assigning the Same Value to Multiple Variables

x = y = z = 100

print(x)
print(y)
print(z)

100
100
100

Variable Naming Rules

Variables follow the same rules as Python identifiers.

• A variable name can contain letters, digits and underscore.
• It cannot start with a digit.
• Spaces are not allowed in variable names.
• 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

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

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 the Value of a Variable

The value stored in a variable can be changed by assigning a new value.

score = 50
print(score)

score = 80
print(score)

50
80

Using Variables in Expressions

Variables can be used in mathematical expressions and calculations.

a = 10
b = 20

sum = a + b
product = a * b

print("Sum =", sum)
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

After del x, the variable x no longer exists.

Constants in Python

Python does not have a special keyword for declaring constants. By convention, names written in uppercase are used to indicate values that should not normally be changed.

PI = 3.14159
MAX_MARKS = 100

print(PI)
print(MAX_MARKS)

Local and Global Variables

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

x = 10

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

display()

10
20

Checking the Type of a Variable

The type() function is used to determine the data type of a variable.

value = 25

print(type(value))

<class 'int'>