Python reversed mapping / dictionary with unhashable type?

Question

I've created a dictionary like

d = {1: {"a":1, "b":2}, 2: {"a":1, "b":2}}

I'm looping through objects to create dictionaries like the above.

I also want to create a reverse of the above dictionary while I loop, it should look like

d2 = {{"a":1, "b":2}: 1, {"a":1, "b":2}: 2}

I know that the dictionary is an unhashable type, but at the same time I want the ability to reverse look up values without looping through the dictionary.

Is there some way to do this in python?

What is the mapping for `{"a":1, "b":2}`, 1 or 2? See [this question](http://stackoverflow.com/questions/1151658/python-hashable-dicts) on making dicts hashable. — khachik, Feb 28 '13 at 06:36
@GrijeshChauhan: There are other things to be considered. See my answer — Abhijit, Feb 28 '13 at 06:40
@Abhijit Yes thats why I posted comment and answer. and vote you — Grijesh Chauhan, Feb 28 '13 at 06:41

Abhijit · Accepted Answer · 2013-02-28T06:37:36.207

I also want to create a reverse of the above dictionary while I loop, it should look like

No, you can't. All keys to a dictionary should be hash-able and a dictionary is not hash-able
Key's cannot have duplicate entries

Is there some way to do this in python?

Unless you wan't the key's to be dictionary, you can convert to some other data structure. May be frozenset of item lists?

If you need duplicate keys, use frozenset of item lists with MultiMap 1.0.3

And google returned me an implementation of frozen dict, you can use it with MultiMap 1.0.3

Python reversed mapping / dictionary with unhashable type?

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