Python嵌套列表 - 更改和替换单个项目

Question

我正在完成一个简单的编程练习（我还是新的），其中我通过为4个不同的字符属性分配30个点来创建角色配置文件。计划功能包括：显示当前配置文件，创建新配置文件或更改现有配置文件。第一个和第二个功能工作正常，但最后一个问题：该程序是为了解开嵌套列表项目（属性+分配的分数），要求新的分数，采取旧的和新的差异，并改变数字相应的池中可用点数。最后，在位置0处向列表添加一个新条目（属性+新分配的分数），然后删除位置1处的条目，该条目应该是该属性的旧条目。遍历列表并完成。但是，一旦执行代码，您将看到它不起作用。请参阅下面的完整代码：

options = ["Strength", "Health", "Wisdom", "Dexterity"] 
profile = [] 
points = 30 

choice = None 
while choice != "0": 

    print(
     """ 
    CHARACTER CREATOR PROGRAM 

    0 - Exit 
    1 - See current profile 
    2 - Build new profile 
    3 - Amend existing profile 

    """ 
     ) 

    choice = input("Please choose an option: ") 
    print() 

    if choice == "0": 
     print("Good bye.") 
    elif choice == "1": 
     for item in profile: 
      print(item) 
     input("\nPress the enter key to continue.") 
    elif choice == "2": 
     print("You can now equip your character with attributes for your adventures.") 
     print("You have",points,"points to spent.") 
     print("Now configure your character: \n") 
     #Run the point allocation loop 
     for item in options: 
      point_aloc = int(input("Please enter points for " + str(item) + ":")) 
      if point_aloc <= points: 
       entry = item, point_aloc 
       profile.append(entry) 
       points = points - point_aloc 
       print("\nYour current choice looks like this: ") 
       print(profile) 
       input("\nPress the enter key to continue.") 
      else: 
       print("Sorry, you can only allocate", points," more points!") 
       print("\nYour current choice looks like this: ") 
       print(profile) 
       input("\nPress the enter key to continue.") 
     print("\nWell done, you have configured your character as follows: ") 
     for item in profile: 
      print(item) 
     input("Press the enter key to continue.") 
    elif choice == "3": 
     print("This is your current character profile:\n") 
     for item in profile: 
      print(item) 
     print("\nYou can change the point allocation for each attribute.") 
     for item in profile: 
      point_new = int(input("Please enter new points for " + str(item) + ":")) 
      attribute, points_aloc = item 
      diff = points_aloc - point_new 
      if diff >0: 
       points += diff 
       print("Your point allocation has changed by", -diff,"points.") 
       print(diff,"points have just been added to the pool.") 
       print("The pool now contains", points,"points.") 
       entry = item, point_new 
       profile.insert(0, entry) 
       del profile[1] 
       input("Press the enter key to continue.\n") 
      elif diff <0 and points - diff >=0: 
       points += diff 
       print("Your point allocation has changed by", -diff,"points.") 
       print(-diff,"points have just been taken from the pool.") 
       print("The pool now contains", points,"points.") 
       entry = item, point_new 
       profile.insert(0, entry) 
       del profile[1] 
       input("Press the enter key to continue.\n") 
      elif diff <0 and points - diff <=0: 
       print("Sorry, but you don't have enough points in the pool!") 
       input("Press the enter key to continue.\n") 
    else: 
     print("Sorry, but this is not a valid choice!") 
     input("Press the enter key to continue.\n") 

input("\n\nPress the enter key to exit.") 

注意：您需要先创建配置文件以运行更改。

在此先感谢您的帮助！

Answer 1

正如您对问题的评论所指出的，您并未以最佳方式提出您的问题。但是，我发现它有什么问题。我可以告诉你如何解决你当前的代码，但事实是，解决这个问题的方法是完全重写它。当您这样做时，您应该采用以下策略：

1. 将代码分解为多个部分。在这种情况下，我建议你创建几个不同的功能。一个可以被称为main_loop，并将包含循环菜单的逻辑。它不包含更新或显示配置文件的任何代码。相反，它会调用其他函数，display_profile,build_profile和amend_profile。这些函数将接受变量，如options,profile和points，并返回值如options和points。这将极大地简化您的代码，并使测试和调试变得更加容易。这是一个什么样main_loop可能看起来像一个例子：

   def main_loop(): 
       options = ["Strength", "Health", "Wisdom", "Dexterity"] 
       profile = [] 
       points = 30 
   
       choice = None 
       while choice != "0": 
        print(menu_string) #define menu_string elsewhere 
        choice = input("Please choose an option: ") 
        print() 
   
        if choice == "0": 
         print("Good bye.") 
        elif choice == "1": 
         display_profile(profile) 
        elif choice == "2": 
         profile, points = build_profile(options, profile, points) 
        elif choice == "3": 
         profile, points = amend_profile(profile, points) 
        else: 
         print("Sorry, but this is not a valid choice!") 
         input("Press the enter key to continue.\n") 
   
       input("\n\nPress the enter key to exit.") 
   

   看到多少更好这是什么？现在您只需定义其他功能即可。像...

   def build_profile(options, profile, points): 
        # insert logic here 
        return profile, points 
   

   这种方法的另一个好处是，现在你可以单独测试这些功能，而无需运行整个程序。

2. 使用正确的成语进行列表修改。在迭代时修改列表需要格外小心，并且在某些情况下（例如，通过删除或添加已经迭代的项目来更改列表的长度），它根本无法工作。有些方法可以对profile做些什么，但对于初学程序员，我会推荐一些更简单的方法：只需创建一个新列表！然后返回该列表。因此，在您amend_profile功能，做这样的事情：

   def amend_profile(profile, points): 
        # other code ... 
        new_profile = [] 
        for item in profile: 
         attribute, points_aloc = item 
         # other code ... 
         new_proflie.append(entry) 
        # other code ... 
   
        return new_profile, points 
   

   还请注意，这是你的主要缺陷之一;您将创建一个entry，其中包含(item, point_new)而不是(attribute, point_new)，因此您的新元组中有一个item元组，而不是如预期的那样只有一个attribute字符串。