python中的倒排字典

Question

我有这本字典

{'jackie chan': ('rush hour', 'rush hour 2'), 
 'crish tucker': ('rush hour', 'rush    hour 2')}

我希望倒排字典是

{'rush hour': ('jackie chan', 'crish tucker'), 
 'rush hour 2': ('jackie chan', 'crish tucker')}

我已经得到了要求逆的函数，但它看起来不像第二本字典

def invert_actor_dict(actor_dict):
    movie_dict = {}
    for key,value in actor_dict.iteritems():

        for actor in value:
            if actor in movie_dict:
                movie_dict[actor].append(key)
            else:
                movie_dict[actor] = (key)
    return movie_dict

Answer 1

您可以使用collections.defaultdict轻松实现这一点

def invert_dict(d):
    inverted_dict = collections.defaultdict(set)
    for actor, movies in d.iteritems():
        for movie in movies:
            inverted_dict.add(actor)
    return inverted_dict

Answer 2

您的代码有两个问题

您遇到的第一个问题位于以下几行：

if actor in movie_dict:
    movie_dict[actor].append(key)
else:
    movie_dict[actor] = (key)

当您编写movie_dict[actor] = (key)时，您并不是在创建一个元组-括号只是为了优先。要创建元组，您必须在末尾添加一个逗号：

 movie_dict[actor] = (key,)

无论如何，这并不能很好地工作，因为元组是不可变的。您应该使用列表：

if actor in movie_dict:
    movie_dict[actor].append(key)
else:
    movie_dict[actor] = [key] # Square brackets

或者创建新的元组：

if actor in movie_dict:
    movie_dict[actor] = movie_dict[actor] + (key,)
else:
    movie_dict[actor] = (key,)

我强烈建议您使用第一个选项。如果您确实需要使用元组，请在处理后将列表转换为元组。

的第二个问题是您似乎期望的

'rush hour 2'

等于

'rush    hour 2'

如字典中所示：

{'jackie chan': 
    ('rush hour', 'rush hour 2'), 
 'crish tucker': 
    ('rush hour', 'rush    hour 2')}

但事实并非如此：

>>> 'rush hour 2' == 'rush    hour 2'
False

你怎么解决这个问题呢？嗯，我设计的最简单的解决方案是在空格处拆分字符串，然后只用一个空格重新连接它：

def invert_actor_dict(actor_dict):
    movie_dict = {}
    for key,value in actor_dict.iteritems():
        for actor in value:
            split_movie_name = key.split()
            # 'rush     hour 2'.split() == ['rush', 'hour', '2']
            movie_name = " ".join(split_movie_name)
            # " ".join(['rush', 'hour', '2']) == 'rush hour 2'
            if actor in movie_dict:
                movie_dict[actor].append(movie_name)
            else:
                movie_dict[actor] = [movie_name]
    return movie_dict

Answer 3

def invert_actor_dict(actor_dict):
   movie_dict = {}
   for actor,movies in actor_dict.iteritems(): 

       for movie in movies:
           if not movie_dict.has(movie):
               movie_dict[movie]=[]
           movie_dict[movie].append(actor)
   return movie_dict