Python Tutorial - While Loop

1. while Loop Example
2. while Loop With else

In this section, we will walk you through while loop that executes a number of statements for a specified number of times.

In a while loop, if the condition is True, control enters into the body of while and statements inside are executed. This process continues until the condition becomes False.

while loop is mostly used when you don’t know how many times the statements are going to be executed (total number of iterations).

The following is the syntax of Python while loop:

while condition:
    block of statements

Here, if the condition is True, control enters the body of while and the block of statements is executed. When the condition becomes False, the iteration will be stopped and the loop is terminated.

while Loop Example

The following program calculates the sum of the first five even numbers:

sum = 0
i = 0  # initializing counter variable at 0
while i <= 10:
    sum = sum + i
    i = i + 2  # incrementing counter variable with inter of 2 for even numbers
print("Sum of the first five even numbers =", sum)

Sum of the first five even numbers = 30

Firstly, you need to initialize the value of your counter variable i. Then you have while loop containing a condition which tells that the loop should be terminated if i becomes greater than 10. Then counter variable i is incremented by adding 2 in each iteration which will generate even numbers as initially i was zero.

When i becomes 12, the loop is terminated and the sum is printed. In each iteration of the loop, the value of i is added to sum.

while Loop With else

In a while loop, you can also have an else part which will be executed when the condition of while is evaluated to be False.

count = 0
while count < 4:
    print("You are inside while loop")
    count = count + 1
else:
    print("You are in else part")

You are inside while loop
You are inside while loop
You are inside while loop
You are inside while loop
You are in else part

When count becomes greater than 4, else part is executed.