Efficient way to convert a list to dictionary

Question

I need help in the most efficient way to convert the following list into a dictionary:

l = ['A:1','B:2','C:3','D:4']  

At present, I do the following:

mydict = {}
for e in l:
    k,v = e.split(':')
    mydict[k] = v

However, I believe there should be a more efficient way to achieve the same. Any idea ?

Answer 1

use dict() with a generator expression:

>>> lis=['A:1','B:2','C:3','D:4']
>>> dict(x.split(":") for x in lis)
{'A': '1', 'C': '3', 'B': '2', 'D': '4'}

Using dict-comprehension ( as suggested by @PaoloMoretti):

>>> {k:v for k,v in (e.split(':') for e in lis)}
{'A': '1', 'C': '3', 'B': '2', 'D': '4'}

Timing results for 10**6 items:

>>> from so import *
>>> %timeit case1()
1 loops, best of 3: 2.09 s per loop
>>> %timeit case2()
1 loops, best of 3: 2.03 s per loop
>>> %timeit case3()
1 loops, best of 3: 2.17 s per loop
>>> %timeit case4()
1 loops, best of 3: 2.39 s per loop
>>> %timeit case5()
1 loops, best of 3: 2.82 s per loop

so.py:

a = ["{0}:{0}".format(i**2) for i in xrange(10**6)]

def case1():
    dc = {}
    for i in a:
        q, w = i.split(':')
        dc[q]=w

def case2():
    dict(x.split(":") for x in a)


def case3():
    {k:v for k,v in (e.split(':') for e in a)}

def case4():
    dict([x.split(":") for x in a])

def case5():
    {x.split(":")[0] : x.split(":")[1] for x in a}

Answer 2

>>> dict(map(lambda s: s.split(":"), ["A:1", "B:2", "C:3", "D:4"]))
{'A': '1', 'C': '3', 'B': '2', 'D': '4'}