Use slice notation with collections.deque

Question

How would you extract items 3..6 efficiently, elegantly and pythonically from the following deque without altering it:

from collections import d         


        

Answer 1

you can override the __getitem__ method and create a SliceableDeque using islice.

There are edge cases, you should consider (for example using negative slices doesn't work with islice).

here is what I have been using:

import itertools
from collections import deque

class SliceableDeque(deque):
    def __getitem__(self, s):
        try:
            start, stop, step = s.start or 0, s.stop or sys.maxsize, s.step or 1
        except AttributeError:  # not a slice but an int
            return super().__getitem__(s)
        try:  # normal slicing
            return list(itertools.islice(self, start, stop, step))
        except ValueError:  # incase of a negative slice object
            length = len(self)
            start, stop = length + start if start < 0 else start, length + stop if stop < 0 else stop
            return list(itertools.islice(self, start, stop, step))