The execution of programming language codes is done by a compiler. A compiler is given a set of codes or rather a sequence of codes that perform a desired task. The task may or may not be repetitive but the compiler is smart enough to process it. Such repetitive code is known as a 'loop'.

Loop is a sequential set of instructions which gets executed multiple times to reduce minimize the repetition of code.
In Python, we have two types of loops :
i. for loop
ii. while loop

To understand the functioning and flow of a loop, you must get familiar with the term 'block'. A block is the smallest unit in a loop which performs one particular task.

'For' loop :

Syntax :

for object in range(initialization, limit, update ):
statements

The above given syntax is of for loop where we put the object name after 'for' and the limit inside 'range( )'.

Program:


Output :
0
1
2
3
4

'While' loop :

Syntax :

while expression:
statements

The above statement is for while loop, where the testing condition is placed after while and it is followed by the statements placed in the loop body.
Program:



Output:

Hello people
Hello people
Hello people

Program:



Output:

hello geek
hello geek
..........

Nested loops :

A nested loop is an inner loop in the loop body of the outer loop. The inner or outer loop can be any type, such as a while loop or for loop. For example, the outer for loop can contain a while loop and vice versa

Program:



Output:

1
2 2
3 3 3
4 4 4 4

Program:



Output:

1 Outer loop is executed only once
1 Inner loop is executed until to completion
2 Inner loop is executed until to completion
2 Outer loop is executed only once
1 Inner loop is executed until to completion
2 Inner loop is executed until to completion