我有一个迭代的解决方案-工作得更好的大字典&很多(例如jsons等):

import collections


def merge_dict_with_subdicts(dict1: dict, dict2: dict) -> dict:
    """
    similar behaviour to builtin dict.update - but knows how to handle nested dicts
    """
    q = collections.deque([(dict1, dict2)])
    while len(q) > 0:
        d1, d2 = q.pop()
        for k, v in d2.items():
            if k in d1 and isinstance(d1[k], dict) and isinstance(v, dict):
                q.append((d1[k], v))
            else:
                d1[k] = v

    return dict1

注意，这将使用d2中的值来覆盖d1，以防它们都不是字典。(与python的dict.update()相同)

一些测试:

def test_deep_update():
    d = dict()
    merge_dict_with_subdicts(d, {"a": 4})
    assert d == {"a": 4}

    new_dict = {
        "b": {
            "c": {
                "d": 6
            }
        }
    }
    merge_dict_with_subdicts(d, new_dict)
    assert d == {
        "a": 4,
        "b": {
            "c": {
                "d": 6
            }
        }
    }

    new_dict = {
        "a": 3,
        "b": {
            "f": 7
        }
    }
    merge_dict_with_subdicts(d, new_dict)
    assert d == {
        "a": 3,
        "b": {
            "c": {
                "d": 6
            },
            "f": 7
        }
    }

    # test a case where one of the dicts has dict as value and the other has something else
    new_dict = {
        'a': {
            'b': 4
        }
    }
    merge_dict_with_subdicts(d, new_dict)
    assert d['a']['b'] == 4

我已经测试了大约1200个字典——这种方法花了0.4秒，而递归的解决方案花了2.5秒。

换个答案怎么样?!?这也避免了突变/副作用:

def merge(dict1, dict2):
    output = {}

    # adds keys from `dict1` if they do not exist in `dict2` and vice-versa
    intersection = {**dict2, **dict1}

    for k_intersect, v_intersect in intersection.items():
        if k_intersect not in dict1:
            v_dict2 = dict2[k_intersect]
            output[k_intersect] = v_dict2

        elif k_intersect not in dict2:
            output[k_intersect] = v_intersect

        elif isinstance(v_intersect, dict):
            v_dict2 = dict2[k_intersect]
            output[k_intersect] = merge(v_intersect, v_dict2)

        else:
            output[k_intersect] = v_intersect

    return output

dict1 = {1:{"a":{"A"}}, 2:{"b":{"B"}}}
dict2 = {2:{"c":{"C"}}, 3:{"d":{"D"}}}
dict3 = {1:{"a":{"A"}}, 2:{"b":{"B"},"c":{"C"}}, 3:{"d":{"D"}}}

assert dict3 == merge(dict1, dict2)

这个版本的函数将处理N个字典，并且只处理字典——不能传递不恰当的参数，否则将引发TypeError。合并本身解释了键冲突，它不是覆盖来自合并链下的字典的数据，而是创建一组值并追加到该值;没有数据丢失。

它可能不是页面上最有效的，但它是最彻底的，当你合并2到N字典时，你不会丢失任何信息。

def merge_dicts(*dicts):
    if not reduce(lambda x, y: isinstance(y, dict) and x, dicts, True):
        raise TypeError, "Object in *dicts not of type dict"
    if len(dicts) < 2:
        raise ValueError, "Requires 2 or more dict objects"


    def merge(a, b):
        for d in set(a.keys()).union(b.keys()):
            if d in a and d in b:
                if type(a[d]) == type(b[d]):
                    if not isinstance(a[d], dict):
                        ret = list({a[d], b[d]})
                        if len(ret) == 1: ret = ret[0]
                        yield (d, sorted(ret))
                    else:
                        yield (d, dict(merge(a[d], b[d])))
                else:
                    raise TypeError, "Conflicting key:value type assignment"
            elif d in a:
                yield (d, a[d])
            elif d in b:
                yield (d, b[d])
            else:
                raise KeyError

    return reduce(lambda x, y: dict(merge(x, y)), dicts[1:], dicts[0])

print merge_dicts({1:1,2:{1:2}},{1:2,2:{3:1}},{4:4})

输出:{1:[1,2]，2:{1:2,3:1}，4:4}

当然，代码将取决于您解决合并冲突的规则。这里有一个版本，它可以接受任意数量的参数，并递归地将它们合并到任意深度，而不使用任何对象突变。它使用以下规则来解决合并冲突:

字典优先于非字典值({"foo":{…}}优先于{"foo": "bar"}) 后面的参数优先于前面的参数(如果按顺序合并{"a": 1}， {"a"， 2}和{"a": 3}，结果将是{"a": 3})

try:
    from collections import Mapping
except ImportError:
    Mapping = dict

def merge_dicts(*dicts):                                                            
    """                                                                             
    Return a new dictionary that is the result of merging the arguments together.   
    In case of conflicts, later arguments take precedence over earlier arguments.   
    """                                                                             
    updated = {}                                                                    
    # grab all keys                                                                 
    keys = set()                                                                    
    for d in dicts:                                                                 
        keys = keys.union(set(d))                                                   

    for key in keys:                                                                
        values = [d[key] for d in dicts if key in d]                                
        # which ones are mapping types? (aka dict)                                  
        maps = [value for value in values if isinstance(value, Mapping)]            
        if maps:                                                                    
            # if we have any mapping types, call recursively to merge them          
            updated[key] = merge_dicts(*maps)                                       
        else:                                                                       
            # otherwise, just grab the last value we have, since later arguments    
            # take precedence over earlier arguments                                
            updated[key] = values[-1]                                               
    return updated  

class Utils(object):

    """

    >>> a = { 'first' : { 'all_rows' : { 'pass' : 'dog', 'number' : '1' } } }
    >>> b = { 'first' : { 'all_rows' : { 'fail' : 'cat', 'number' : '5' } } }
    >>> Utils.merge_dict(b, a) == { 'first' : { 'all_rows' : { 'pass' : 'dog', 'fail' : 'cat', 'number' : '5' } } }
    True

    >>> main = {'a': {'b': {'test': 'bug'}, 'c': 'C'}}
    >>> suply = {'a': {'b': 2, 'd': 'D', 'c': {'test': 'bug2'}}}
    >>> Utils.merge_dict(main, suply) == {'a': {'b': {'test': 'bug'}, 'c': 'C', 'd': 'D'}}
    True

    """

    @staticmethod
    def merge_dict(main, suply):
        """
        获取融合的字典，以main为主,suply补充,冲突时以main为准
        :return:
        """
        for key, value in suply.items():
            if key in main:
                if isinstance(main[key], dict):
                    if isinstance(value, dict):
                        Utils.merge_dict(main[key], value)
                    else:
                        pass
                else:
                    pass
            else:
                main[key] = value
        return main

if __name__ == '__main__':
    import doctest
    doctest.testmod()

在不影响输入字典的情况下返回一个合并。

def _merge_dicts(dictA: Dict = {}, dictB: Dict = {}) -> Dict:
    # it suffices to pass as an argument a clone of `dictA`
    return _merge_dicts_aux(dictA, dictB, copy(dictA))


def _merge_dicts_aux(dictA: Dict = {}, dictB: Dict = {}, result: Dict = {}, path: List[str] = None) -> Dict:

    # conflict path, None if none
    if path is None:
        path = []

    for key in dictB:

        # if the key doesn't exist in A, add the B element to A
        if key not in dictA:
            result[key] = dictB[key]

        else:
            # if the key value is a dict, both in A and in B, merge the dicts
            if isinstance(dictA[key], dict) and isinstance(dictB[key], dict):
                _merge_dicts_aux(dictA[key], dictB[key], result[key], path + [str(key)])

            # if the key value is the same in A and in B, ignore
            elif dictA[key] == dictB[key]:
                pass

            # if the key value differs in A and in B, raise error
            else:
                err: str = f"Conflict at {'.'.join(path + [str(key)])}"
                raise Exception(err)

    return result

灵感来自@andrew cooke的解决方案