将列表列表转换为字典

Question

I have the following list of list:

[[u'3', u'4'], [u'4', u'5'], [u'7', u'8'], [u'1', u'2'], [u'2', u'3'], [u'6', u'7'], [u'5', u'6']]

I want to obtain:

{3:'4', 4:'5', 7:'8', 1:'2', 2:'3', 6:'7', 5:'6'}

List could be long, so it needs to be more efficient as possible.

The first element of each "pair" [[first, second], ...] is unique, so we can make a dictionary from it.

I tried with the following, but I think it will be slow:

def getdict(l):
    result = {}
    for e in l:
        result[int(e[0])] = e[1]
    return result

Answer 1

You can use a dictionary comprehension :

>>> l = [[u'3', u'4'], [u'4', u'5'], [u'7', u'8'], [u'1', u'2'], [u'2', u'3'], [u'6', u'7'], [u'5', u'6']]
>>> {int(key): value for key, value in l}
{1: u'2', 2: u'3', 3: u'4', 4: u'5', 5: u'6', 6: u'7', 7: u'8'}

Note that you would "lose" duplicates like in the @Kevin's example:

>>> l = [['1', '2'], ['1', '3']]
>>> {int(key): value for key, value in l}
{1: '3'}

Answer 2

my_dict = {}
for item in my_list:
    my_dict[int(item[0])] = item[1]