Python for循环质数

#!/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 factor
         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'
         break