xslice idea | a generator slice

Thu Jul 11 11:14:46 EDT 2013

On 11 July 2013 15:54, Russel Walker <russ.pobox at gmail.com> wrote:
> ...oh and here is the class I made for it.
>> class xslice(object):
> '''
> xslice(seq, start, stop, step) -> generator slice
> '''
>> def __init__(self, seq, *stop):

Wouldn't it be better if it has the same signature(s) as itertools.islice?
> if len(stop) > 3:
> raise TypeError("xslice takes at most 4 arguments")
> elif len(stop) < 0:

How would len(stop) be negative?
> raise TypeError("xslice requires atleast 2 arguments")
> else:
> start, stop, step = (((0,) + stop[:2])[-2:] + # start, stop
> (stop[2:] + (1,))[:1]) # step
> stop = min(stop, len(seq))
> self._ind = iter(xrange(start, stop, step))
> self._seq = seq
>> def __iter__(self):
> return self
>> def next(self):
> return self._seq[self._ind.next()]
>>>> Although now that I think about it, it probably should've just been a simple generator function.

Or you can use itertools.imap:
def xslice(sequence, start_or_stop, *args):
 indices = xrange(*slice(start_or_stop, *args).indices(len(sequence)))
 return imap(sequence.__getitem__, indices)
Oscar