Python Nested Loops

December 26, 2020

Nested Loop

A nested loop is a loop inside another loop. The “inner loop” will be executed one time for each iteration of the “outer loop”.

If outer loop executes M times and inner loop executes N times , the time complexity of the loop will be (M*N).

A final note on loop nesting is that we can put any type of loop inside of any other type of loop. For example a for loop can be inside a while loop or vice versa

Syntax :

For/while (Outer Loop):
- For/while( Inner Loop) :
For/while ( Outer Loop) :
- if and else ( Inner Loop)r

Working :

The outer loop iterates through the range from 0 to n/len(sequence) and for each item in that sequence.
It enters the inner loop where it iterates over a range of that item.
For each iteration of that item, it perform the given operation.
It only leaves the inner loop when it has completely iterated through a range of that item.
When it leaves the inner loop, it goes back to the outer loop and the process continues until it has completely iterated over its sequence.

Example :

#python Program 
#nested Loop

#for-for nested Loop 
for i in range(1,3):
    for j in range(1,6): #print the multiplication of 1 and 2 
        print(i*j,end=‘ ‘)
    print(‘ ‘) 

#for-while nested loop
j=1 
for i in range(1,3):
    j=1
    while(j<6): 
        print(i*j, end =‘ ‘)

        j=j+1 
    print(‘ ‘) 

#while-while nested loop 
i=1
while(i<3):
    j=1 
    while(j<6):
        print(i*j,end=‘ ‘)
        j=j+1 
    print(‘ ‘)
    i+=1 

#while-If nested Loop 
i=1 
j=1 
while(i<3):
    if(j<6):
        print(i*j, end =‘ ‘)
        j=j+1  
    else:
        j=1 
        i+=1
        print(”)