Python 中的多个级别的“collection.defaultdict" [英] Multiple levels of 'collection.defaultdict' in Python

问题描述

感谢 SO 上的一些伟大人物，我发现了 collections.defaultdict 提供的可能性，尤其是在可读性和速度方面.我已经成功地使用了它们.

现在我想实现三个级别的字典，最高的两个是defaultdict，最低的一个是int.我没有找到合适的方法来做到这一点.这是我的尝试:

from collections import defaultdictd = defaultdict(defaultdict)a = [("key1", {"a1":22, "a2":33}),(key2"，{a1":32，a2":55})，("key3", {"a1":43, "a2":44})]因为我在一个:d[i[0]] = i[1]

现在这有效，但以下是所需的行为，但无效:

d["key4"]["a1"] + 1

我怀疑我应该在某处声明第二级 defaultdict 的类型为 int，但我没有找到在哪里或如何这样做.

我首先使用 defaultdict 的原因是为了避免必须为每个新键初始化字典.

还有更优雅的建议吗?

感谢 pythoneers！

解决方案

使用:

from collections import defaultdictd = defaultdict(lambda: defaultdict(int))

每当在 d 中访问新键时，这将创建一个新的 defaultdict(int).

Thanks to some great folks on SO, I discovered the possibilities offered by collections.defaultdict, notably in readability and speed. I have put them to use with success.

Now I would like to implement three levels of dictionaries, the two top ones being defaultdict and the lowest one being int. I don't find the appropriate way to do this. Here is my attempt:

from collections import defaultdict
d = defaultdict(defaultdict)
a = [("key1", {"a1":22, "a2":33}),
     ("key2", {"a1":32, "a2":55}),
     ("key3", {"a1":43, "a2":44})]
for i in a:
    d[i[0]] = i[1]

Now this works, but the following, which is the desired behavior, doesn't:

d["key4"]["a1"] + 1

I suspect that I should have declared somewhere that the second level defaultdict is of type int, but I didn't find where or how to do so.

The reason I am using defaultdict in the first place is to avoid having to initialize the dictionary for each new key.

Any more elegant suggestion?

Thanks pythoneers!

解决方案

Use:

from collections import defaultdict
d = defaultdict(lambda: defaultdict(int))

This will create a new defaultdict(int) whenever a new key is accessed in d.

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