How to convert a tuple list with duplicated keys and values into a fancy dicionary?

Question

I have a tuple list like the code below, an identifier has multiple values(both identifier and values maybe duplicated), I thought using dict with a str as a key and a set as it's value would be reasonable, but how?

tuple_list = [
    ('id1', 123),
    ('id1', 123),
    ('id2', 123),
    ('id1', 456),
    ('id2', 456),
    ('id1', 789),
    ('id2', 789)
]

What I need is like this: { 'id1': {123, 456, 789}, ... }`, my code is:

for id, val in tuple_list:
    map_data[id].append(val) # error here, how to fix this?

Possible duplicate of [Python group by](http://stackoverflow.com/questions/3749512/python-group-by) or [How do I use Python's itertools.groupby()?](http://stackoverflow.com/questions/773/how-do-i-use-pythons-itertools-groupby) — TessellatingHeckler, Aug 04 '16 at 04:22

DurgaDatta · Answer 1 · 2016-08-04T04:40:09.023

1

You can use setdefaultdict:

map_data = {}
for id, val in tuple_list:
    map_data.setdefault(id,set()).add(val)

edited Aug 04 '16 at 04:40

answered Aug 04 '16 at 04:17

DurgaDatta

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OP wants a set not a list. – juanpa.arrivillaga Aug 04 '16 at 04:22
Apologies for the format, I've modified it, thank you. – Elinx Aug 04 '16 at 04:35

score 1 · Accepted Answer · answered Aug 04 '16 at 04:35

To use a dict containing a set do it like this.

from collections import defaultdict

tuple_list = [
    ('id1', 123),
    ('id1', 123),
    ('id2', 123),
    ('id1', 456),
    ('id2', 456),
    ('id1', 789),
    ('id2', 789)
]

map_data = defaultdict(set)

for id, val in tuple_list:
    map_data[id].add(val)

print(map_data)

result

defaultdict(<type 'set'>, {'id2': set([456, 123, 789]), 'id1': set([456, 123, 789])})

How to convert a tuple list with duplicated keys and values into a fancy dicionary?

2 Answers2