重复直到完成

Question

所以我得到了这段代码，我想让它自己重复，直到用户让他的用户名不以符号或数字开头。

  name=name.capitalize()
    print(name)
    surname= input("surname")
    surname=surname.capitalize()
    print(surname)
    password= input("password")
    username= input("username")
    first_char = username[0]
    if first_char.isalpha():
        print('done')
    else: print('username must start with a letter')

Answer 1

我还没有测试过这段代码，但似乎您只需要一个简单的 while 循环，如下所示：

surname = input("surname")
while not surname[0].isalpha():
    print("surname must start with a letter")
    surname = input("surname")

Answer 2

你很接近：

name = input("Name:").capitalize()
print(name)
surname = input("Surname:").capitalize()
password = input("Password:")
username = input("Username:")
while not username[0].isalpha():
print('Done')

选择：

name, surname, password, username = input("Name:").capitalize(), input('Surname:').capitalize(), input('Password'), input('Username')
while not username[0].isalpha():
        print('Username must start with a letter')
print('Done')

Answer 3

如果你使用的是 python 3.8，你可以使用 := 操作符来写这个：

while not (username := input("username: "))[0].isalpha():
    print('username must start with a letter')
# do stuff

否则你的选择将是：

(a) 重复一行代码

username = input("username: ")
while not username[0].isalpha():
    print('username must start with a letter')
    username = input("username: ")
# do stuff

或 (b) 使用 break:

的无限外观

while True:
    username = input("username: ")
    if username[0].isalpha():
        break
    print('username must start with a letter')
# do stuff

重复直到完成

Repeating until done

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