Roy Smith wrote:
> import types
>
> class slicableDict (dict):
> def __getitem__ (self, index):
> if type (index) == types.SliceType:
> d2 = slicableDict()
> for key in self.keys():
> if key >= index.start and key < index.stop:
> d2[key] = self[key]
> return d2
> else:
> return dict.__getitem__ (self, index)
[...]
> Roy-Smiths-Computer:play$ ./slice.py
> {'oysters': 4, 'hen': 1, 'porpoises': 5, 'geese': 3, 'ducks': 2}
> {'hen': 1, 'geese': 3, 'ducks': 2}
>
> I defined d[x:y] as returning a new dictionary which contains those items
> from the original whose keys are in the range x <= key < y. I'm not sure
> this is terribly useful but it's a neat demonstration of just how simple
> Python makes it to do stuff like this. I can't imagine how much work it
> would be to add a similar functionality to something like C++ multimap.
Other possibility, probably faster when almost all keys in the range are in
the dictionary:
class sdict(dict):
def __getitem__(self, index):
if isinstance(index, slice):
d = {}
for key in xrange(slice.start, slice.stop, slice.step):
if key in self:
d[key] = self[key]
return d
else:
return dict.__getitem__(self, index)
Reinhold
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