In the Python programming language, a while loop statement runs a target statement repeatedly as long as a specific condition is true.

Syntax

while expression:

    statement(s)

Example:

#!/usr/bin/python

count = 0

while (count < 7):

   print( 'The count is:', count)

   count = count + 1

print ("bye bye!")

Output:

The count is: 0

The count is: 1

The count is: 2

The count is: 3

The count is: 4

The count is: 5

The count is: 6

bye bye!

The Infinite Loop in Python

If a condition is never FALSE, a loop becomes endless. While loops should be used with caution since it’s possible that this condition will never resolve to a FALSE value. As a result, a never-ending cycle is created. An endless loop is a name given to such a loop.

Example:

var = 1

while var == 1 :  # This constructs an infinite loop

    num = input("Enter a number:")

    print ("You entered: ", num)

print ("Good bye!")

Output:

Enter a number: 20

You entered: 20

Enter a number: 29

You entered: 29

Enter a number: 3

You entered: 3

.

.

.

.

.

Example:

while True :  # This constructs an infinite loop

    num = input("Enter a number:")

    print ("You entered: ", num)

print("Good bye!")

Output:

Enter a number: 20

You entered: 20

Enter a number: 29

You entered:  29

Enter a number: 3

You entered: 3

.

.

While loop with else

Python enables you to use an else statement with a loop statement. When using the else statement with a while loop, it is performed when the condition turns false.

Example:

count = 0

while count < 5:

   print (count, "is  less than 5" )

   count = count + 1

else:

   print(count, "is not less than 5")

Output:

0 is less than 5

1 is less than 5

2 is less than 5

3 is less than 5

4 is less than 5

5 is not less than 5