python中if else流程判断

#!/usr/bin/env python

import getpass   #调用getpass模块就能实现密码密文显示

username=input("username:")
userpasswd=getpass.getpass("userpasswd:")

print(username,userpasswd)

#!/usr/bin/env python

_username = "lijinzhu"
_userpasswd = "abc123"
username = input("username:")
userpasswd = input("userpasswd:")

if _username == username and _userpasswd == userpasswd:
    print("Welcome usr {name} login...".format(name=username))
else:
    print("Invalid username or passwd!")

#!/usr/bin/env python

_age = 18
age = int(input("age:"))

if _age == age:
    print("right")
elif _age > age:
    print("think smaller...")
else:
    print("think strong...")