判断输入的用户名：
#Author:zww
_username = "zww"
_password = "123"
username = input("username:")
password = input("password:")
if username == _username and password == _password:
    print("Welcome {user} login" .format(user=username))
else:
    print("Invalid username or password!")

#Author:zww
age_of_jay = 40
guess_age = int(input("guess_age:"))
if guess_age > age_of_jay:
    print("think smaller..." )
elif guess_age < age_of_jay:
    print("think bigger...")
else:
    print("yes,you got it!")