Greg Ewing <[EMAIL PROTECTED]> wrote:
> Also, everyone, please keep in mind that you always have
> the option of using a *dictionary*, in which case your
> indices can start wherever you want.
>
> You can't slice them, true, but you can't have everything. :-)
Of course you can slice them, you just have to subclass dict! The
following was about 15 minutes work:
---------------
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)
d = slicableDict()
d['hen'] = 1
d['ducks'] = 2
d['geese'] = 3
d['oysters'] = 4
d['porpoises'] = 5
print d
print d['a':'m']
---------------
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.
I'm sure the code above could be improved, and I know I've ignored all
sorts of things like steps, and error checking. Frankly, I'm amazed this
worked at all; I expected to get a syntax error when I tried to create a
slice with non-numeric values.
PS: Extra credit if you can identify the set of keys I used without
resorting to google :-)
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