python 2 3对于sys.stdin时的区别

python 2:

import sys
s=set()
while True:
    line=sys.stdin.readline() ////////1.用while循环 2.必须用sys.stdin.readlin()来获取每行数据
    if not line.strip():
        break
    for i in line.split():
        s.add(i)
print len(s)