每个值有多个键 [英] Multiple keys per value

问题描述

是否可以在 Python 字典中为每个值分配多个键.一种可能的解决方案是为每个键分配值:

Is it possible to assign multiple keys per value in a Python dictionary. One possible solution is to assign value to each key:

dict = {'k1':'v1', 'k2':'v1', 'k3':'v1', 'k4':'v2'}

但这不是内存效率，因为我的数据文件 > 2 GB.否则，您可以制作字典键的字典:

but this is not memory efficient since my data file is > 2 GB. Otherwise you could make a dictionary of dictionary keys:

key_dic = {'k1':'k1', 'k2':'k1', 'k3':'k1', 'k4':'k4'}
dict = {'k1':'v1', 'k4':'v2'}
main_key = key_dict['k2']
value = dict[main_key]

这也很费时间和精力，因为我必须两次浏览整个字典/文件.有没有其他简单的内置 Python 解决方案?

This is also very time and effort consuming because I have to go through whole dictionary/file twice. Is there any other easy and inbuilt Python solution?

注意:我的字典值不是简单的字符串(如问题v1"、v2")，而是复杂的对象(包含不同的其他字典/列表等，无法对它们进行腌制)

注意:问题似乎类似于 如何对同一个字典值同时使用键和索引?但我不是在寻找有序/索引字典，而是在寻找除此问题中提到的两个之外的其他有效解决方案(如果有).

Note: my dictionary values are not simple string (as in the question 'v1', 'v2') rather complex objects (contains different other dictionary/list etc. and not possible to pickle them)

Note: the question seems similar as How can I use both a key and an index for the same dictionary value? But I am not looking for ordered/indexed dictionary and I am looking for other efficient solutions (if any) other then the two mentioned in this question.

推荐答案

值是什么类型?

dict = {'k1':MyClass(1), 'k2':MyClass(1)}

会给出重复的值对象，但是

will give duplicate value objects, but

v1 = MyClass(1)
dict = {'k1':v1, 'k2':v1}

导致两个键都指向同一个实际对象.

results in both keys referring to the same actual object.

在最初的问题中，您的值是字符串:即使您两次声明相同的字符串，我认为在这种情况下它们会被实习到同一个对象

In the original question, your values are strings: even though you're declaring the same string twice, I think they'll be interned to the same object in that case

注意.如果您不确定是否最终得到了重复项，您可以像这样找到:

NB. if you're not sure whether you've ended up with duplicates, you can find out like so:

if dict['k1'] is dict['k2']:
    print("good: k1 and k2 refer to the same instance")
else:
    print("bad: k1 and k2 refer to different instances")

(is 检查感谢 J.F.Sebastian，替换 id())

(is check thanks to J.F.Sebastian, replacing id())

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