合并Python 2.7中的多嵌套词典的最佳方法 [英] The best way to merge multi-nested dictionaries in Python 2.7

问题描述

我有两个嵌套的字典，我想将它们合并为一个(第二个dict覆盖第一个dict值).我看到了许多用于合并平面"(非嵌套)字典的漂亮解决方案，例如:

I have two nested dictionaries and I want to merge them into one (where second dict overrides first dict values). I saw a lot of beautiful solutions for merging "flat" (not nested) dictionaries, e.g.:

dict_result = dict1.copy()
dict_result.update(dict2)

或

dict_result = dict(dict1.items() + dict2.items())

或(我最喜欢的人)

dict_result = dict(d1,**d2)

但找不到最有效的方法来合并多嵌套字典.

but couldn't find the most efficient way to merge multi-nested dicts.

我正在尝试避免递归.你的主张是什么?

I'm trying to avoid recursion. What is your proposition?

推荐答案

除非严格限制合并字典的深度，否则无法避免递归. ¹⁾此外，也没有公告或库函数来执行此操作(也就是说，我所不知道的)，但这实际上并不难.这样的事情应该做:

Unless the depth of the dictionaries to merge is strictly limited, there's no way to avoid recursion.¹⁾ Also, there's no bultin or library function to do this (that is, none that I know of), but it's actually not all that hard. Something like this should do:

def merge(d1, d2):
    for k in d2:
        if k in d1 and isinstance(d1[k], dict) and isinstance(d2[k], dict):
            merge(d1[k], d2[k])
        else:
            d1[k] = d2[k]   

这是什么:迭代d2中的键，并且如果也可以在d1中找到该键并且它们都是字典，则合并这些子字典，否则用<中的值覆盖d1中的值c0>.请注意，这会更改d1及其子字典 ，因此您可能需要对其进行深度复制.

What this does: It iterates the keys in d2 and if the key can also be found in d1 and both are dictionaries, merge those sub-dictionaries, otherwise overwrite the value in d1 with that from d2. Note that this changes d1 and its sub-dictionaries in place, so you might want to deep-copy it before.

或使用此版本创建合并的副本:

Or use this version to create a merged copy:

def merge_copy(d1, d2):
    return {k: merge_copy(d1[k], d2[k]) if k in d1 and isinstance(d1[k], dict) and isinstance(d2[k], dict) else d2[k] for k in d2}

示例:

>>> d1 = {"foo": {"bar": 23, "blub": 42}, "flub": 17}
>>> d2 = {"foo": {"bar": 100}, "flub": {"flub2": 10}, "more": {"stuff": 111}}
>>> merge(d1, d2)
>>> print d1
{'foo': {'bar': 100, 'blub': 42}, 'flub': {'flub2': 10}, 'more': {'stuff': 111}}

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¹⁾您可以使用堆栈进行迭代，但这只会使事情变得更加复杂，并且应该这样做以避免出现最大递归深度的问题.

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¹⁾ You can make it iterative, using a stack, but this will only make things more complicated and should only be done to avoid problems with maximum recursive depth.

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