Assigning intermediate variable in python list comprehension [duplicate]

Question

I have a list of strings (both strings and list can be large). I want to build dictionary out of only certain elements from the list.

l = ['aaa 0','bbb 1','ccc 2','ddd 3','abc 1']
wanted = set(['aaa','abc'])
dict([x.split() for x in l if x.split()[0] in wanted])

{'aaa': '0', 'abc': '1'}

Can this be done without calling split() operation twice?

Answer 1

Using nested generator expression ((x.split() for x in l)) to yield key, value pairs:

>>> l = ['aaa 0', 'bbb 1', 'ccc 2', 'ddd 3', 'abc 1']
>>> wanted = {'aaa', 'abc'}
>>> {key: value for key, value in (x.split() for x in l) if key in wanted}
{'abc': '1', 'aaa': '0'}