Python – While Loop

Python – While Loop: A loop statement allows a programme to repeat a set of instructions under certain conditions. This allows a programmer to build programmes with fewer lines of code and improve the readability of the code. To meet looping requirements, Python includes the following types of loops:

• while loop
• for loop

The While Loop

The Python – While Loop allows you to repeat a group of statements as long as a certain condition is true. It may be thought of as a looping if statement. When the number of iterations is unknown, a while loop is chosen over a for loop.

Syntax

while condition:
  statements

Flow Diagram:

In the example below, the programme utilises a while loop to add all numbers from 1 to 5.

sum = 0
i = 1
while (i < 6):
  sum = sum + i
  i = i+1
print(sum)

The output of the above code will be:

15

While loop with else statement

The else block can also be used inside a while loop. When the condition check in the while loop returns false, the else block is invoked.

Syntax

while condition:
  statements
else:
  statements

After exiting the while loop, the else code block is executed in the example below.

i = 1
while (i < 6):
  print(i)
  i = i + 1
else:
  print('loop exhausted.')

The output of the above code will be:

1
2
3
4
5
loop exhausted.

When the programme exits the while loop using break statements, however, the else block is ignored.

i = 1
while (i < 6):
  print(i)
  i = i + 1
  if (i==4):
    break
else:
  print('loop exhausted.')

The output of the above code will be:

1
2
3

Also Read: Java – While Loop