python - Multiple keys per value

Question

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'}

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]

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?

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.

Answer 1

What type are the values?

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

will give duplicate value objects, but

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

results in both keys referring to the same actual object.

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

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