flip keys and values in dictionary python

Question

I have a dictionary called z that looks like this

---

{0: [0.28209479177387814, 0.19947114020071635, 0.10377687435514868, 0.07338133158686996], -1: [0.282094791773878

Answer 1

You can't have duplicate keys in a dictionary, but you can pair them together using tuples in a meaningful way.

from itertools import product, chain

tuples = chain.from_iterable(product(vs, [k]) for k, vs in orig_dict.items())
# note this is identical to:
# # tuples = []
# # for k, vs in orig_dict.items():
# #     for tup in [(v, k) for v in vs]:
# #         tuples.append(tup)

That will produce:

[(0.28209479177387814, 0), (0.19947114020071635, 0),
 (0.10377687435514868, 0), (0.07338133158686996, 0),
 (0.28209479177387814, -1), (0.19947114020071635, -1),
 (0.10377687435514868, -1), (0.07338133158686996, -1)]

Now if you really wanted something interesting, you could sort that and group it together.

from itertools import groupby

groups = groupby(sorted(tuples), key=lambda kv: kv[0])

That creates something like:

[(0.07338133158686996, [(0.07338133158686996, 0,
                         0.07338133158686996, -1] ),
 ... ]

You could toss those into a dict by doing:

final_dict = {k: [v[1] for v in vs] for k, vs in groups}

Which should finally give:

{0.07338133158686996: [0, -1],
 ... }