python学习：利用循环语句完善输入设置

利用循环语句完善输入设置

使用for循环：

代码1：_user = "alex"_password = "abc123"

for i in range(3):    username = input("Username:")    password = input("Password:")    if username == _user and password == _password:        print("Welcome %s login ..." % _user)        break    else:        print("Invalid username or password !")代码2：

_user = "alex"_password = "abc123"

passed_authentication = False

for i in range(3):    username = input("Username:")    password = input("Password:")    if username == _user and password == _password:        print("Welcome %s login ..." % _user)        passed_authentication = True #真，成立        break    else:        print("Invalid username or password !")

if not passed_authentication:    print("您的输入次数已经达到上限！") #只有在True的情况下，条件成立

 代码3：

_user = "alex"_password = "abc123"

#passed_authentication = False

for i in range(3):    username = input("Username:")    password = input("Password:")    if username == _user and password == _password:        print("Welcome %s login ..." % _user)        #passed_authentication = True #真，成立        break    else:        print("Invalid username or password !")else:    print("您的输入次数已经达到上限！")#for循环正常结束，就可以执行下面的else语句

原文地址：https://www.cnblogs.com/pl-2018/p/9419186.html