Why isn't the output match with my expected output? Python dictionary

Question

I tried to add the string elements to the dictionary but it doesnt work

adatok = ["marha", 1, "kacsa", 2, "kacsa", 1, "birka", 3, "marha", 4, "marha", 2]
sorszámok = list(set([x for x in adatok if type(x) == int]))


szótár = {}
for i in sorszámok:#Létrehozzuk a sorszámokat egy szótárba
    szótár.update({i:set()})

for j in adatok:
    if type(j) == int:
        szótár[j].add(adatok[adatok.index(j)-1])
#Expected output:{1: {'marha','kacsa'}, 2: {'kacsa','marha'}, 3: {'birka'}, 4: {'marha'}}
#Output:{1: {'marha'}, 2: {'kacsa'}, 3: {'birka'}, 4: {'marha'}}

Answer 1

Instead of starting with unique keys and then trying to find the values for each key, iterate over the key, value pairs and add them to the sets. Using defaultdict saves you the trouble of setting up the dict ahead of time.

>>> from collections import defaultdict
>>> adatok = ["marha", 1, "kacsa", 2, "kacsa", 1, "birka", 3, "marha", 4, "marha", 2]
>>> szótár = defaultdict(set)
>>> for k, v in zip(adatok[1::2], adatok[0::2]):
...     szótár[k].add(v)
...
>>> dict(szótár)
{1: {'marha', 'kacsa'}, 2: {'marha', 'kacsa'}, 3: {'birka'}, 4: {'marha'}}