python - 初学者Python用户: trouble with error code - too many values to unpack (expected 2)

Question

该程序旨在接收用户名和密码并验证它们。我现在只查看用户名部分。

这是我的功能:

def valid_username(username):
    if not username.isalpha():
        reason = ('username can only contain alpha numeric numbers')
        return reason

    numupper =0
    for c in username:
        if not c.isupper():
            numupper = numupper + 1

        if numupper <= 0:
            reason=('username must contain at least one uppercase character')
            return reason

    numlower =0
    for c in username:
        if not c.islower():
            numlower = numlower + 1

        if numlower <= 0:
            reason=('username must contain at least one lowercase character')
            return reason

        if len(username)<8:
            reason = ('username must be greater than 8 characters')
            return reason

    numdigit=0
    for c in username:
        if not c.isdigit():
            numdigit = numdigit + 1

        if numdigit <= 0:
            reason= ('username must contain at least one number')
            return reason

这是我的程序:

import uservalidation

# get a username from the user
username = input("Username: ")

# validate username
result, reason = uservalidation.valid_username(username)

# if it isn't valid we should tell them why
if not(result):
    print (reason)

(the next else is the password part)

但我收到此错误代码:

Traceback (most recent call last):
  File "/Users/katiemoore/Documents/MooreKatie_assign9.py", line 7, in <module>
    result, reason = uservalidation.valid_username(username)
ValueError: too many values to unpack (expected 2)

我真的不知道这是什么意思，有人可以帮忙吗？

Answer 1

函数valid_username仅返回一个字符串reason。但是您在函数调用时收到两个参数。因此出现了错误。因此，返回一个空字符串是合适的，因为分配给 result 变量将是正确的

而不是

return reason

使用

return '',reason

这会起作用