How to use while loop repetition control in python with examples

There are two types of repetition control instructions in python.

1. while loop
2. for loop
   

1.) while Loop:

• A while loop allows a part of code to be executed as long as the given condition is true.
• The while loop is used to repeatedly execute instructions as long as expression is true.
• A while loop is used in the case where the number of iterations is not know in advance.

The while loop has two syntax (forms):

a.) while condition:

         statement 1

         statement 2

         statement 3    

b.) while condition:

          statement 1

          statement 2

     else:

         statement 3

         statement 4

Note:-else block of codes will be executed when condition fails.

Program 1 : Write a python program to add the given numbers.

sum=0
num=int(input("Enter the last number upto which you want to add:\n"))
i=1
while(i<=num):
    sum =sum+i
    i=i+1
print("The sum of all numbers is= ",sum)

Output:-

Program 2 : Write a python program to print the given numbers.

num=int(input("Enter the number:"))
i=1
while(i<=num):
    print(i)
    i=i+1

Output:-

Infinite while loop:-

• When any while loop condition never become false then while while loop will never terminate.This is called infinite condition.
• Any non-zero values in while loop indicates always true condition and whereas zero indicates the always false condition.

Program 3 : While infinite loop:

num=int(input("Enter non zero number:"))
while(num):
    print("welcome to MNT LAB")

Output:-

Program 4 : While infinite loop:

import time
a=1
num=int(input("Enter a value:\n"))
while(1):
    n=a+num
    a=a+1
    time.sleep(2)
    print(n)

Output:-

Use the else statement in while loop:-

• The else block is executed when the condition given in while loop becomes false.
• If the while loop is terminated using break statement then else block of codes will not be executed and statement present after the else block will be executed.

Program 5 :Write a python program to print the list values.

list=[1,2,3,4,5,6,7,8,9,10]
i=0
while(i<10):
    print(list[i])
    i=i+1

Output:-

Program 6 : Write a python program to print the given numbers.

i=1
num=int(input("Enter the Number upto which you want to print: \n"))
while(i<=num):
    print(i)
    i=i+1
else:
    print("While loop is terminated...")

Output:-

Program 7 : Write a python program to print the some numbers out of given numbers.

i=1
num=int(input("Enter the Number upto which you want to print: \n"))
while(i<=num):
    print(i)
    if(i==8):
        break
    i=i+1
else:
    print("While loop is termineted...")

Output:-

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