diy2.py

username = "python"
userpassword = "123456"
cishu=5
while True:
    name = input("请输入用户名:")
    password = input("请输入密码:")
    if name == username and password == userpassword:
        print("登录成功!")
        break
    else:
        if cishu==0:
            exec()
        if username!=name:
            if username!=name and userpassword!=password:
                cishu-=1
                print("用户名和密码错误!请重新输入")
                print("您还剩"+str(cishu)+"次机会。")
            else:
                cishu-=1
                print("用户名错误!请重新输入")
                print("您还剩"+str(cishu)+"次机会。")        
        else:
            cishu-=1               
            print("密码错误!请重新输入")
            print("您还剩"+str(cishu)+"次机会。")    
print("欢迎来到贝尔编程!")