Python While Loop

Python While Loop is used to execute a set of statements repeatedly based on the result of a condition.

When condition is True, the set of statements are executed, and when the condition is False, the loop is broken and the program control continues with the rest of the statements in program.

In this tutorial, we will learn how to write While Loop statement in Python, and how to use while loop with the help of example programs.

Syntax

The syntax of Python While Loop is

while condition :
    statement(s)

The statement(s) are executed repeatedly in loop, as long as the condition is True. The condition is a boolean expression that should return or atleast implicitly typecast to boolean value.

Flowchart of While Loop in Python

The following is a flowchart to the flow of execution of While Loop. The loop is depicted in blue lines.

Python While Loop

Example

While Loop Statement to Print Multiples of 3

In the following program, we have a while loop statement that prints multiples of 3 in the range of 3 to 30.

Example.py

i=1
while i < 11:
    print(3*i)
    i=i+1
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Output

3
6
9
12
15
18
21
24
27
30

Nested While Loop

The body of while loop consists of statements. And these statements could be another while loop, If statement, If-Else statement or For Loop statement or any valid Python statement.

Print Start Pattern using Nested While Loop

In the following example, we will write a while loop statement inside another while loop. Its like while in while which is nested while loop. Using this nested while loop, we print a start pattern.

Example.py

i=1
while i < 11:
    j = 0
    while j < i:
        print('*',end='')
        j=j+1
    print()
    i=i+1
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Output

*
**
***
****
*****
******
*******
********
*********
**********

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While Loop with Break

Python Break statement can be used inside a looping statement to break the loop even before condition becomes False.

In the following example, we have a while loop statement. The while loop has a break statements that executes conditionally when i becomes 7. And inside this if-statement we have break statement. This break statement breaks the while loop.

Example.py

i = 1
while i <= 100 :
    print(i)
    if i == 7 :
        break
    i += 1
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Output

1
2
3
4
5
6
7

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While Loop with Continue

Python Continue statement can be used to skip the execution of further statements in while loop body and continue with next iteration of while loop.

In this example, we shall write a Python program with while loop to print numbers from 1 to 20. But, when we get an odd number, we will continue the loop with next iterations.

Example.py

i = 0
while i <= 20 :
    i += 1
    if i % 2 == 1 :
        continue
    print(i)
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Make sure that you update the control variables participating in the while loop condition, before you execute the continue statement.

Output

2
4
6
8
10
12
14
16
18
20

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Python Infinite While Loop

Infinite while loop is a loop in which the condition is always True and never comes out of the loop.

Example.py

while True:
    print("hello")
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Output

hello
hello
hello
hello

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Python Programs based on While Loop

Following are references to some of the tutorials that use while loop in different scenarios.

Conclusion

In this Python Tutorial, we learned what a while loop is, its syntax, working mechanism of While loop, nested while loop and much more with examples.