List of tuples to dictionary
PythonListDictionaryTuplesPython Problem Overview
Here's how I'm currently converting a list of tuples to dictionary in Python:
l = [('a',1),('b',2)]
h = {}
[h.update({k:v}) for k,v in l]
> [None, None]
h
> {'a': 1, 'b': 2}
Is there a better way? It seems like there should be a one-liner to do this.
Python Solutions
Solution 1 - Python
Just call dict() on the list of tuples directly
>>> my_list = [('a', 1), ('b', 2)]
>>> dict(my_list)
{'a': 1, 'b': 2}
Solution 2 - Python
It seems everyone here assumes the list of tuples have one to one mapping between key and values (e.g. it does not have duplicated keys for the dictionary). As this is the first question coming up searching on this topic, I post an answer for a more general case where we have to deal with duplicates:
mylist = [(a,1),(a,2),(b,3)]
result = {}
for i in mylist:
result.setdefault(i[0],[]).append(i[1])
print(result)
>>> result = {a:[1,2], b:[3]}
Solution 3 - Python
The dict constructor accepts input exactly as you have it (key/value tuples).
>>> l = [('a',1),('b',2)]
>>> d = dict(l)
>>> d
{'a': 1, 'b': 2}
From the documentation:
> For example, these all return a > dictionary equal to {"one": 1, "two": > 2}: > > dict(one=1, two=2) > dict({'one': 1, 'two': 2}) > dict(zip(('one', 'two'), (1, 2))) > dict([['two', 2], ['one', 1]])
Solution 4 - Python
With dict comprehension:
h = {k:v for k,v in l}
Solution 5 - Python
Functional decision for @pegah answer:
from itertools import groupby
mylist = [('a', 1), ('b', 3), ('a', 2), ('b', 4)]
#mylist = iter([('a', 1), ('b', 3), ('a', 2), ('b', 4)])
result = { k : [*map(lambda v: v[1], values)]
for k, values in groupby(sorted(mylist, key=lambda x: x[0]), lambda x: x[0])
}
print(result)
# {'a': [1, 2], 'b': [3, 4]}