程序如下:

#!/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)

输出如下:

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