python 阶乘 + 计算阶乘末尾有几个零

#coding=utf-8
import re
while 1:
print '[*] --> n! (n>4 and n=N*)'
try:
x=int(input('n=：'))
x=range(x+1)[1:]
y=1
for i in x:
y=i*y
y=str(y)
def count_0(y):
rex=r'(0+\b)'
read=re.findall(rex,y)
return read
a=count_0(y)
except:
print '输入有误！\n'
else:
print '结果：%s\n末尾零数：%d\n'%(y,len(a[0]))