python——if和elif语句练习

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#例子1
username = input("请输入命令：")
password = input("请输入密码：")

if username == "lipc" and password == 123:
    print("登陆成功")
else:
    print("登陆失败")


#例子2
fen = int(input("请输入你的成绩："))
if 0 < fen <= 59:
    print("不及格")
elif 60 <= fen <= 79:
    print("较好")
elif 80 <= fen <= 99:
    print("优秀")
elif fen == 100:
    print("满分")
else:
    print("无效的输入")


#例子3
year = int(input("请输入年："))
month = int(input("请输入月份："))
if  month == 1 or  month == 3 or  month == 5 or  month == 7 or  month == 8 or  month == 10 or  month == 12:
    print("此月有 31 天。")
elif  month == 4 or  month == 6 or  month == 9 or  month == 11:
    print("此月有 30 天。")
elif month == 2 and ((year % 4==0 and year % 100!=0) or (year % 400==0)):
    print('29天')
else:
    print('28天')