八、循环【下载网站：你好msdn】

输入密码时，密码看不见，即密文：

import getpass

#导入getpass标准库，直接调用就可以密文

username = input("username:")
password = getpass.getpass("password:")
print(username,password)

if/else循环

_username='alex'
_password='abc123'
username=input("username:")
password=input("password:")

if _username ==username and _password== password:
    print("Welcome user {name} login...".format(name=username))
else:
    print("Invalid username or password!")

小游戏：猜数字，猜年龄

age_of_oldboy = 56

guess_age = int(input("guess age:"))    

if guess_age == age_of_oldboy :
    print("yes, you got it.")
elif guess_age > age_of_oldboy:
    print("think smaller...")
else:
    print("think bigger!")

猜3次，猜对了就结束，错了就3次机会，用完就没有了。

age_of_oldboy = 56

guess_age = input("gusee age:")