Using non-hashable Python objects as keys in dictionaries

Question

Python doesn\'t allow non-hashable objects to be used as keys in other dictionaries. As pointed out by Andrey Vlasovskikh, there is a nice workaround for the special case of

Answer 1

Based off solution by Chris Lutz. Note that this doesn't handle objects that are changed by iteration, such as streams, nor does it handle cycles.

import collections

def make_hashable(obj):
    """WARNING: This function only works on a limited subset of objects
    Make a range of objects hashable. 
    Accepts embedded dictionaries, lists or tuples (including namedtuples)"""
    if isinstance(obj, collections.Hashable):
        #Fine to be hashed without any changes
        return obj
    elif isinstance(obj, collections.Mapping):
        #Convert into a frozenset instead
        items=list(obj.items())
        for i, item in enumerate(items):
                items[i]=make_hashable(item)
        return frozenset(items)
    elif isinstance(obj, collections.Iterable):
        #Convert into a tuple instead
        ret=[type(obj)]
        for i, item in enumerate(obj):
                ret.append(make_hashable(item))
        return tuple(ret)
    #Use the id of the object
    return id(obj)