Octavian Rasnita wrote in news:0db6c288b2274dbba5463e7771349...@teddy in
gmane.comp.python.general:
> Hi,
>
> If I want to create a dictionary from a list, is there a better way
> than the long line below?
>
> l = [1, 2, 3, 4, 5, 6, 7, 'a', 8, 'b']
>
> d = dict(zip([l[x] for x in range(len(l)) if x %2 == 0], [l[x] for x
> in range(len(l)) if x %2 == 1]))
>
> print(d)
>
> {8: 'b', 1: 2, 3: 4, 5: 6, 7: 'a'}
>>> dict( zip( l[ :: 2 ], l[ 1 :: 2 ] ) )
{8: 'b', 1: 2, 3: 4, 5: 6, 7: 'a'}
If you don't know about slice notation, the synatax I'm using above is:
list[ start : stop : step ]
where I have ommited the "stop" item, which defaults to the length of the
list.
<http://docs.python.org/library/stdtypes.html#sequence-types-str-unicode-
list-tuple-bytearray-buffer-xrange>
That will make 3 lists before it makes the dict thought, so if the
list is large:
>>> dict( ( l[ i ], l[ i + 1 ] ) for i in xrange( 0, len( l ), 2 ) )
may be better.
Rob.
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