创建和查找每个值具有多个键的2D词典 [英] Create and lookup 2D dictionary with multiple keys per value

问题描述

我想我要制作一个二维字典，每个值有多个键.

I think I want to make a 2D dictionary with multiple keys per value.

我知道如何使用defaultdict制作2D词典:

I know how to make a 2D dictionary using defaultdict:

from collections import defaultdict
2d_dict = defaultdict(dict)

2d_dict['canned_food']['spam'] = 'delicious'

我知道，使用常规词典，您可以使用多个键来制作，例如:

And I know that using regular dictionaries you can make with multiple keys like:

dictionary={('food','canned_food'):spam}

但是我想做一些类似的事情，例如通过键元组查找

But I want to do something like lookup by tuple-of-keys:

2d_dict[('canned_food','food')]['spam'] = 'delicious'

在字典的第一个维度中，每个值需要25个键.有没有办法用defaultdict做到这一点?

In the first dimension of dictionary I need ~25 keys per value. Is there a way to do this with defaultdict?

即使有方法可以用字典来做，这是否是制作简单的多维查找表的合理方法呢?

Even if there is a way to do it with dicts is this a reasonable way to make a simple multidimensional lookup table?

推荐答案

除了2d_dict是无效的变量名(以数字开头)之外，您现有的解决方案已经有效:

Apart from 2d_dict being an invalid variable name (it starts with a digit), your existing solution already works:

>>> from collections import defaultdict
>>> d2_dict = defaultdict(dict)
>>> d2_dict[('canned_food', 'food')]['spam'] = 'delicious'
>>> d2_dict
defaultdict(<type 'dict'>, {('canned_food', 'food'): {'spam': 'delicious'}})

实际上，您甚至不需要括号-Python仍会将您的键识别为元组:

In fact, you don't even need the parentheses - Python will still recognise your key as a tuple:

>>> d2_dict['fresh_food', 'food']['eggs'] = 'delicious'
>>> d2_dict
defaultdict(<type 'dict'>, {('canned_food', 'food'): {'spam': 'delicious'},
('fresh_food', 'food'): {'eggs': 'delicious'}})

...，是的，这是构建2D + 1D查找表的一种完全合理的方法.

... and, yes, it's a perfectly reasonable way to build a 2D+1D lookup table.

如果您要使用嵌套字典而不是元组键构建3D查找表，则可以使用该功能:

If you want to build a 3D lookup table using nested dicts instead of tuple keys, this works:

>>> d3_dict = defaultdict(lambda: defaultdict(dict))
>>> d3_dict['dried_food']['food']['jerky'] = 'chewy'
>>> d3_dict
defaultdict(<function <lambda> at 0x7f20af38a2a8>, 
{'dried_food': defaultdict(<type 'dict'>, {'food': {'jerky': 'chewy'}})})

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