比较字典，更新而不覆盖值[重复]

I am not寻找这样的东西：

如何将两个字典合并到一个表达式中？ https://stackoverflow.com/questions/38987/how-do-i-merge-two-dictionaries-in-a-single-expression

更新Python字典而不覆盖子字典的通用方法 https://stackoverflow.com/questions/22093793/generic-way-of-updating-python-dictionary-without-overwriting-the-subdictionarie?lq=1

Python：如果值存在，则通过更新但不覆盖来合并字典 https://stackoverflow.com/questions/6354436/python-dictionary-merge-by-updating-but-not-overwriting-if-value-exists

I am寻找这样的东西：

input:

d1 = {'a': 'a', 'b': 'b'}
d2 = {'b': 'c', 'c': 'd'}

output:

new_dict = {'a': ['a'], 'b': ['b', 'c'], 'c': ['d']}

我有以下代码哪个有效但我想知道是否有更有效的方法：

首先，我创建一个列表“unique_vals”，其中存储两个字典中存在的所有值。 由此，创建一个新字典，其中存储两个字典中存在的所有值

unique_vals = []
new_dict = {}
for key in list(d1.keys())+list(d2.keys()) :
    unique_vals = []
    try:
        for val in d1[key]:
            try:
                for val1 in d2[key]:
                    if(val1 == val) and (val1 not in unique_vals):
                        unique_vals.append(val)
            except:
                continue
    except:        
        new_dict[key] = unique_vals
    new_dict[key] = unique_vals

然后，对于两个字典中未在此新字典中列出的每个值，这些值将附加到新字典中。

for key in d1.keys():
      for val in d1[key]:
          if val not in new_dict[key]:
              new_dict[key].append(val)
for key in d2.keys():
    for val in d2[key]:
        if val not in new_dict[key]:
            new_dict[key].append(val)

也许与defaultdict?

>>> d1 = {'a': 'a', 'b': 'b'} 
>>> d2 = {'b': 'c', 'c': 'd'}
>>> from collections import defaultdict                                         
>>>                                                                             
>>> merged = defaultdict(list)                                                  
>>> dicts = [d1, d2]                                                            
>>> for d in dicts: 
...:     for key, value in d.items(): 
...:         merged[key].append(value) 
...:                                                                            
>>> merged                                                                      
defaultdict(list, {'a': ['a'], 'b': ['b', 'c'], 'c': ['d']})

这适用于任意数量的词典dicts list.

作为一个函数：

def merge_dicts(dicts):
    merged = defaultdict(list)

    for d in dicts:
        for key, value in d.items():
            merged[key].append(value)

    return merged