else和with

一 else 1.和if搭配 2.和while/for搭配，循环顺利完成后执行else（break跳出后不会被执行） 3.try语句没有异常执行else 二 with 1.自动关闭文件

try: with open('date.txt','w') as f: for each_line in f: print(each_line) except OSError as reason: print('出错啦：'+str(reason))