The else Statement Used with Loops

Python supports to have an else statement associated with a loop statements.

·         If the else statement is used with a for loop, the else statement is executed when the loop has exhausted iterating the list.

·         If the else statement is used with a while loop, the else statement is executed when the condition becomes false.

Example:

The following example illustrates the combination of an else statement with a for statement that searches for prime numbers from 10 through 20.

#!/usr/bin/python

For num in range (10, 20):      #to iterate between  10  to  20

     For i in range  (2,  num)  : #to iterate on the factors of the number

            If  num% I == 0:           #to determine the first facto

               J = num/I                  #to calculate the second factor

              Print  ‘%d equals  %d * %d ‘  % (num, i, j)

              break             #to move to the next number, the #first FOR

else:                             #else part of the loop

print  num,  ‘is a prime number’

This  will produce following result:

10 equals 2*5

11 is a prime number

12 equals 2*6

13 is a prime number

14 equals 2*7

15 equals 3*5

16 equals 2*8

17 is a prime number

18 equals 2*9

19 is a prime number.