更新 Python 类中的列表

Question

我想更新一个列表以包含用户添加的新项目。有一些条件，例如代码长度必须为 7 位。如果代码已经存在，系统会通知用户。如果用户尝试使用不同的代码添加另一个“up”副本，系统将不允许这样做。这将使他们再次尝试，因为代码必须相同。最终我将包含一个视频编号，因此如果有两个“up”副本，它们将有两个不同的视频编号但相同的视频代码。

谁能告诉我为什么下面的代码不适合我？

all_movies = []

class Movie(object):
    movie_list = []


    def __init__(self, code, title, director):
        self.code = code
        self.title = title
        self.director = director

        Movie.movie_list.append(self)

    @staticmethod
    def add_movie():

        mv_code = input("Code of movie: ")
        movie_code = int(mv_code)
        movie_title = input("Name of movie: ")
        movie_director = input("Director: ")

        if len(mv_code) == 7:
           all_movies.append(Movie(movie_code, movie_title, movie_director))

           print("movie added to database")
        else:
            print("the code must be 7 digits long, add movie again.")

        def check_validity(movie_code, all_movies):
            if movie_code in all_movies:
                return True
            else:
                return False

        if check_validity(movie_code, all_movies):
            all_movies[all_movies] += Movie
            print()
            print("updated")
        else:
            all_movies[movie_code] = [movie_code, movie_title, movie_director]

def main():
    movie1 = Movie(1122334, 'Up', 'Director')
    movie2 = Movie(1231235, 'Taxi Driver', 'Film-maker')

这是我收到的错误消息：

all_movies[movie_code] = [movie_code, movie_title, movie_director] 
IndexError: list assignment index out of range

Answer 1

首先，这种结构不适合您的愿望。
关于你得到的错误，我应该说你必须将所有电影定义为字典而不是列表（因为你想为每部电影使用）。
试试这个：

all_movies = {}

在你add_movie方法：

@staticmethod
def add_movie():

    mv_code = input("Code of movie: ")
    movie_code = int(mv_code)
    movie_title = input("Name of movie: ")
    movie_director = input("Director: ")

    if len(mv_code) == 7:
       if movie_code in all_movies.keys():
           print("the movie already exists")
           # what do you want to happen here ? 
       else:
           all_movies[movie_code] = (movie_code, movie_title, movie_director)
           print("movie added to database")
    else:
        print("the code must be 7 digits long, add movie again.")

这将向all_movies 添加一部电影，您不需要其余的代码，而且我不明白init 和movie_list 的用法。
试试这个，然后告诉我如果电影中已经存在代码会发生什么，我会为你更新我的答案。

更新：

根据您在评论中的愿望，该方法将更新为如下内容：

@staticmethod
def add_movie():

    mv_code = input("Code of movie: ")
    movie_code = int(mv_code)
    movie_title = input("Name of movie: ")
    movie_director = input("Director: ")

    if len(mv_code) == 7:
       if movie_code in all_movies.keys():
           print("the movie is already exists, adding it with another video number")
           # all_movies[movie_code][-1] is the last video with an existing key
           # all_movies[movie_code][-1][-1] last video number generated
           new_video_number = all_movies[movie_code][-1][-1] + 1
           all_movies[movie_code].append([movie_title, movie_director, new_video_number]) # adding it with new video number
           print("movie added to database with new video number")        
       else:
           all_movies[movie_code] = []
           all_movies[movie_code].append([movie_title, movie_director, 1]) # 1 is the first movie added(video number)
           print("movie added to database")
    else:
        print("the code must be 7 digits long, add movie again.")

这将像这样返回all_movies：

{
    '1231235':[
        ['Taxi Driver', 'Film-maker', 1]
    ]
    '1122334':[
        ['Up', 'Director',1],
        ['Up', 'Director',2],
        ['Up', 'Director',3],
   ]
    '1122333':[
        ['Another movie', 'Another Director',1],
        ['Another movie', 'Another Director',2],
   ]
}

内部列表的最后一个元素是系统自动生成的video_numbers。