In this post, we will learn about if-else and nested if-else in python with an easy and simple example. So let’s start learning what is if-else and nested if-else in python.

## what is if-else in python?

if-else is a keyword in python and it is used as a conditional block in which when the condition is true then if block is executed otherwise else block is executed.

Let’s take an example to understand the if-else block in python

``````number = int(input("ENter a number: "))
if number>5:
print("number is greater then five")
else:
print("number is not greater then five")``````

Output-1:

``````ENter a number: 6
number is greater then five``````

Output-2:

``````ENter a number: 4
number is not greater then five``````

## Expaination

In the above example, the `number` is checked in the `if `block, and when a condition is true then code inside the `if` block is executed otherwise code inside the `else` block is executed.

that means `if` block is executed when your condition is true.

## Important note while using if-else in python

1. `else` block is always written after `if `block (it is compulsory).
2. you can write only `if `block.
3. you can not write only `else` block (it will give an error because` else` block is always written after` if `block).
4. you can write more than one condition in `if` block using logical operators.

Let’s take an example to understand all the above notes of the if-else block.

## only if statement

``````num = int(input("ENter a any number: "))
if num>7:
print("number is greater then seven")
``````

Output:

``````ENter a any number: 9
number is greater then seven``````

if a condition is not true then the above code does nothing (Because there is no else block).

## only else statement gives error

``````num = input("ENter your name: ")
else:
print("this is else block")``````

Output:

``````Desktop\allinpython\if-else.py", line 2
else:
^
SyntaxError: invalid syntax``````

`else` block is always written after `if` block otherwise it will give SyntaxError.

## if statement with multiple conditions

``````num = int(input("ENter a any number: "))
if num>4 and num<6:
print("entered number is five")
else:
print("entered number is not five")``````

Output-1:

``````ENter a any number: 6
entered number is not five``````

Output-2:

``````ENter a any number: 5
entered number is five``````

Now i hope so you understand all the basic concept of if-else in python, So it is time to start learning nested if-else in python.

## what is nested if-else in python

A if-else statement placed inside another `if` or `else` statement is know as nesting of if-else.

let’s understand nested if-else with the help of example:

``````num1 = int(input("Enter any number: "))
if num1>10:
if num1<15:
print("number is less than 15")
else:
print("number is greater than 15")

else:
if num1<5:
print("number is less than 5")
else:
print("number is greater than 5")``````

Output-1:

``````Enter any number: 11
number is less than 15``````

Output-2:

``````Enter any number: 7
number is greater than 5`````` 