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The while Statement

In Python, you use the while statement to specify code that is to be executed as long as a specified condition is true. Because this code can execute more than once, the while statement is sometimes referred to as a loop.

Here is a simple example of a loop created using while:

# display the numbers from 1 to 10
x = 1
while x <= 10:
	print x
	x = x + 1

In this example, the while statement checks whether x is less than or equal to 10. (As before, x <= 10 is the conditional expression for the loop.) If it is, the value of x is printed, and 1 is added to x. The process is repeated until x becomes greater than 10. Because x starts at 1, the loop is executed ten times, and the code displays the numbers from 1 to 10.

The while statement uses the same comparison operators as the if statement. The statements included with the while condition must be indented.

	When using the while statement, make sure that the loop will eventually be terminated. Here is an example of a loop that never terminates: # display the numbers from 1 to 10 x = 1 while x <= 10: print x In this example, the value of x is set to 1 and never changed. This means that the while condition is always true. This loop will execute forever or until you kill off the process that is running it.