Variables in Python

What is a Variable?

A variable is used to store data in memory.

Example:

name = "Aditya"
age = 25

Here:

• name stores text
• age stores a number

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Rules for Naming Variables

Valid Examples

student_name = "Rahul"
age2 = 20
_total = 500

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Invalid Examples

2name = "Rahul"     # Cannot start with number
student-name = "A"  # Hyphen not allowed

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Multiple Variable Assignment

x, y, z = 10, 20, 30
print(x, y, z)

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Dynamic Typing

Python automatically detects data type.

x = 10
x = "Hello"

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Data Types in Python

Python has several built-in data types.

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1. Integer (int)

Integers are whole numbers.

age = 25
marks = -90

print(type(age))

Output:

<class 'int'>

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2. Float (float)

Float represents decimal numbers.

price = 99.99
pi = 3.14

Output:

<class 'float'>

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3. String (str)

String stores text.

name = "Aditya"
city = 'Delhi'

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String Examples

print(name)
print(city)

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4. Boolean (bool)

Boolean has only two values:

• True
• False

is_logged_in = True
is_admin = False

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5. Complex (complex)

Complex numbers contain real and imaginary parts.

x = 3 + 5j

print(type(x))

Output:

<class 'complex'>

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Checking Data Type

Use type() function.

x = 10
print(type(x))

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Type Conversion

Type conversion means changing one data type into another.

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1. Integer to Float

x = 10
y = float(x)

print(y)

Output:

10.0

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2. Float to Integer

x = 5.9
y = int(x)

print(y)

Output:

5

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3. Integer to String

x = 100
y = str(x)

print(y)
print(type(y))

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4. String to Integer

x = "50"
y = int(x)

print(y + 10)

Output:

60

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Input and Output

Output using print()

print("Welcome to Python")

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Taking Input from User

name = input("Enter your name: ")

print("Hello", name)

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Input Always Returns String

age = input("Enter age: ")

print(type(age))

Output:

<class 'str'>

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Convert Input to Integer

age = int(input("Enter age: "))

print(age + 5)

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Operators in Python

Operators are used to perform operations on values and variables.

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1. Arithmetic Operators

Operator	Meaning	Example
+	Addition	5 + 2
-	Subtraction	5 - 2
*	Multiplication	5 * 2
/	Division	5 / 2
%	Modulus	5 % 2
**	Power	5 ** 2
//	Floor Division	5 // 2

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Example

a = 10
b = 3

print(a + b)
print(a - b)
print(a * b)
print(a / b)
print(a % b)
print(a ** b)
print(a // b)

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2. Comparison Operators

Used to compare values.

Operator	Meaning
==	Equal
!=	Not equal
>	Greater than
<	Less than
>=	Greater than equal
<=	Less than equal

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Example

x = 10
y = 20

print(x == y)
print(x != y)
print(x > y)
print(x < y)

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3. Logical Operators

Used with conditions.

Operator	Meaning
and	Both conditions true
or	Any one condition true
not	Reverse condition

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Example

age = 20

print(age > 18 and age < 30)
print(age > 18 or age < 10)
print(not(age > 18))

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4. Assignment Operators

Used to assign values.

Operator	Example
=	x = 5
+=	x += 2
-=	x -= 2
*=	x *= 2
/=	x /= 2

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Example

x = 10

x += 5
print(x)

x *= 2
print(x)

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5. Bitwise Operators

Operate on binary values.

Operator	Meaning
&	AND
`	`
^	XOR
~	NOT
<<	Left Shift
>>	Right Shift

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Example

a = 5
b = 3

print(a & b)
print(a | b)
print(a ^ b)

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6. Membership Operators

Used to check membership in sequence.

Operator	Meaning
in	Present
not in	Not present

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Example

text = "Python"

print("P" in text)
print("z" not in text)

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7. Identity Operators

Used to compare memory location.

Operator	Meaning
is	Same object
is not	Different object

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Example

x = [1, 2]
y = x
z = [1, 2]

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

Output:

True
False