如何在make_user_choice函数的while循环中正确返回user_input变量？

我尝试在make_user_choice函数的while循环中返回user_input变量，但不清楚正确的实现方式，当前代码运行出现异常。

原代码 #

import random
"""Supports a round of rock, paper, scissors between a user and a computer."""

user_input = input("Choose one: rock, paper, scissors? ")

def make_user_choice():
    """Returns the user's choice of rock, paper, or scissors if it is correct."""
    while user_input != "rock" or user_input != "paper" or user_input != "scissors":
        print("that is not a valid imput. please try again")
        break
        return user_input
    return user_input

def make_computer_choice():
    """Returns the computer's random choice of rock, paper, or scissors."""
    choice = random.randint(1,3)
    if choice == 1:
        return "rock"
    elif choice == 2:
        return "paper"
    if choice == 3:
        return "scissors"

def wins_matchup(choice, opponent_choice):
    """Returns True if the first player's choice wins over their opponent.
    Choices can be rock, paper, or scissors. Assumes the choices are different.
    """
    return choice == "rock"

def format_score(user_score, computer_score):
    """Returns a formatted version of the players's current scores."""
    return ">> Score: " + str(user_score) + "-" + str(computer_score)

运行输出 #

Choose one: rock, paper, scissors? rtgyhuji
that is not a valid imput. please try again
rtgyhuji (you) vs. rock
Computer wins!
>> Score: 0-1
that is not a valid imput. please try again
rtgyhuji (you) vs. paper
Computer wins!
>> Score: 0-2

问题分析与修正 #

核心错误点： #

1. 全局变量误用：user_input定义在函数外，属于全局变量，一旦输入错误值，函数内不会重新获取新输入，导致错误值一直被重复使用。
2. 循环条件逻辑错误：while user_input != "rock" or user_input != "paper" or user_input != "scissors" 用了or，任何值都不可能同时等于三个选项，导致循环条件永远为真，失去校验意义。应该换成and，表示输入不是三个选项中的任意一个时才循环。
3. break语句无效：break直接跳出循环，导致无法重新获取输入，循环校验的作用完全失效。
4. return语句位置错误：break后的return永远不会被执行，正确逻辑应该是在循环内反复获取输入，直到输入有效后再返回。

修正后的make_user_choice函数 #

def make_user_choice():
    """Returns the user's choice of rock, paper, or scissors if it is correct."""
    while True:
        user_input = input("Choose one: rock, paper, scissors? ")
        if user_input in ["rock", "paper", "scissors"]:
            return user_input
        print("that is not a valid input. please try again")

同时需要删除全局的user_input = input(...)语句，因为输入逻辑已经整合到函数内部。

其他可优化点： #

• wins_matchup函数逻辑不完整，当前仅判断了choice == "rock"，补充完整胜负规则：

  def wins_matchup(choice, opponent_choice):
      """Returns True if the first player's choice wins over their opponent.
      Choices can be rock, paper, or scissors. Assumes the choices are different.
      """
      winning_pairs = {
          "rock": "scissors",
          "paper": "rock",
          "scissors": "paper"
      }
      return winning_pairs[choice] == opponent_choice
  

• make_computer_choice可以简化为直接从列表随机选择：

  def make_computer_choice():
      """Returns the computer's random choice of rock, paper, or scissors."""
      return random.choice(["rock", "paper", "scissors"])
  

内容的提问来源于stack exchange，提问作者nathan