Python实现求最大公约数及判断素数的方法

#!/usr/bin/env python 
def showMaxFactor(num): 
  count = num / 2  
  while count > 1: 
    if num % count == 0: 
      print 'largest factor of %d is %d' % (num, count) 
      break    #break跳出时会跳出下面的else语句 
    count -= 1 
  else: 
    print num, "is prime" 
for eachNum in range(10,21): 
  showMaxFactor(eachNum) 

largest factor of 10 is 5
11 is prime
largest factor of 12 is 6
13 is prime
largest factor of 14 is 7
largest factor of 15 is 5
largest factor of 16 is 8
17 is prime
largest factor of 18 is 9
19 is prime
largest factor of 20 is 10