The while loop in Python provide us the utility to execute a particular set of statements repeatedly until the required condition is fulfilled.

Syntax

while(conditions):
    Statements

How it works

Firstly, Python interpreter looks out for the condition, if the given condition is True, then it will execute all the statements inside the loop. Once all the statements gets executed, it will go back and check the condition again. It will keep doing so, as long as condition remains True. And when this condition gets false, control is send out of the loop.

Let us code an example to perform the implementation of while loop.

Program : Program to display the counting from 1 to 10 using while loop.

i = 1
# loop to print counting from 1 to 10
while i <= 10:
    print(i, end=' ')
    i += 1

Let us consider one more program using while loop

Program : To evaluate the sum of digits of a number.

n = 23417
sums = 0
# loop to traverse each digit of a number
while n > 0:
    # finding remainder when number is divided by 10
    rem = n % 10
    # adding the remainder obtained 
    sums = sums + rem
    # dividing the number by 10 to access next digit of a number
    n //= 10
print("Sum of digits : ", sums)

Explanation

Let the number be 23417 so our task is to evaluate 2+3+4+1+7. We can do so by finding the remainder of a number(adding it to sum),divide it with 10 until the number gets 0. For this we need a ‘while’ loop which will run till ‘n>0’.In each iteration we perform three steps :
1. rem=n%10; //rem=23417%10=7
2. sum=sum+rem; //sum=7
3. n=n/10; //num=23417/10=2341
Hence on repeating these steps(till n>0), we get the sum of digits of a number.

Hope you now got the complete picture.

That’s all, see you in the next lecture.