尽管具有有效值作为输入，程序仍拒绝运行“if”语句

Question

我是计算机编程的新手，目前正在 PyCharm Community 中编写一个程序，当给出我学校学生的名字时，它会打印出从学校到该学生家的路线。一切都进行得很顺利，昨晚我得到了它的基础。今天我打开我的电脑，出于某种原因，我的程序拒绝运行我的“if”/“elif”语句，并且只会运行 else 语句，即使它的值满足“if”/“elif”语句。我试过重写程序，多次重启 PyCharm，确保我的空格和制表符一致，并确保我的变量都可以相互通信。我已经在这里和其他网站上搜索了一段时间，但我只是看不出为什么我的代码昨天能正常工作但现在除了 else 语句之外拒绝运行任何东西。这是我的代码，它会询问用户“你想去哪里？” 然后将收到“房子”的输入。一旦收到此信息，它将打印出他们的指示。取而代之的是，它每次都运行“else”语句。# Storing the names and directions of users:David = "Directions to David's home from T... \n East on X, \n South on Y.," \            " \n West on Z., \n South on A., \n first white house on the right."Caroline = "Directions to Caroline's home from T... \n East on x, \n South on y.," \        " \n East on z., \n South on p., \n East on q," \        " \n West on t., \n last brick house in the cul-de-sac."William = "Directions to Will's home from T... \n East on x, \n South on y.," \        " \n West on z., \n South on Fa., \n West on b., \n first house on the right."Bannon = "<Insert directions to Bannon's house>"# User gives a specific name and then receives a location:while True:    destination = input("Where would you like to go? ")    if destination.casefold() == 'Davids house':        print(David)        continue    elif destination.casefold() == 'Carolines house':        print(Caroline)        continue    elif destination.casefold() == 'Wills house':        print(William)        continue    elif destination.casefold() == 'Bannons house':        print(Bannon)        continue    # If an invalid location is given, this code will run:    else:        print("Sorry, that location wasn't found! Please try again.")        continue

Answer 1

casefold将字符串转换为小写，并且您的参考字符串包含大写字符。

作为一个简单的修复，您可以将“Davids house”更改为“davids house”等。

从长远来看，您可能希望实现稍微不那么脆弱的比较，但这是一项艰巨的任务，并且取决于您的程序将如何使用以及解析失败的后果是什么。

Answer 2

对于拼写错误纠正和支持用户做破坏测试的事情，下面是一个使用字符串相似性比较来确定输入是否接近任何用户名的示例：

import difflib

# Storing the names and directions of users: 

#This is called a dictionary. More info here https://www.w3schools.com/python/python_dictionaries.asp

directions= {

    "David": "Directions to David's home from T... \n East on X, \n South on Y.," \

            " \n West on Z., \n South on A., \n first white house on the right.",

    "Caroline": "Directions to Caroline's home from T... \n East on x, \n South on y.," \

        " \n East on z., \n South on p., \n East on q," \

        " \n West on t., \n last brick house in the cul-de-sac.",

    "William":"Directions to Will's home from T... \n East on x, \n South on y.," \

        " \n West on z., \n South on Fa., \n West on b., \n first house on the right.",

    "Bannon":"<Insert directions to Bannon's house>"

}

# User gives a specific name and then receives a location:

while True:

    destination = input("Where would you like to go? ")

    highest = 0 #highest score between the user name and input

    user_key = "" #name of the user who most closely matches the input

    for user in directions: #iterate through all the user's names in the directions dictionary

      similarity = difflib.SequenceMatcher( #for each user's name, compare it to the input

          None, destination, user).ratio()

      if(similarity > highest): #if the similarity score is greater than the highest recorded score, update the score

        highest = similarity

        user_key = user

    

    #Code that runs if a match is too low are not found

    if(highest < 0.5): #adjust this based on how close you want the match to be. highest will always be between 0.0 and 1.0

      print("Sorry, that location wasn't found! Please try again.")

      continue

    #Print user's directions

    else:

      print('\n\nGetting directions to ' + user_key + '\'s house\n\n')

      print(directions[user_key] + "\n\n\n")

因此，如果您输入“William's house”、“William”、“William's house”、“Williamm”或接近“William”的名称，您将获得前往 William 家的路线。

Answer 3

最小化程序并测试！您发布的代码多于演示问题所需的代码。一旦出现if destination.casefold() == 'Davids house':无法正常工作的情况，请尽量减少罐装数据的问题

destination = "david's house"

if not destination.casefold() == "Davids house":

    print(repr(destination), "failed")

这打印

"david's house" failed

帮助casefold说Return a version of the string suitable for caseless comparisons. . 啊，就是这样。你需要把两边都折叠起来。然后是那个讨厌的撇号。也许您需要更多规范化，例如摆脱非字母字符。

通过最小化，您为代码编写了一个很好的测试。您可以编写一个小的比较函数来执行 casefold 和其他规范化。然后，您可以对该函数编写十几个测试来测试所有边缘情况。