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

I'd add this as a new answer, to provide better formatting.

For simplicity, Shawn's answer is perfect, but if you often need to get a slice from dequeue, you might prefer to subclass it and add a __getslice__ method.

from collections import deque
from itertools import islice
class deque_slice(deque):
    def __new__(cls, *args):
        return deque.__new__(cls, *args)
    def __getslice__(self, start, end):
        return list(islice(self, start, end))

This won't support setting a new slice, but you can implement your own custom __setslice__ method using the same concept.

NOTE: this is valid for Python <=2.* only. It's also worth noticing that, while __getslice__ is deprecated since python 2.0, the documentation still reports this for the latest 2.7 release:

(However, built-in types in CPython currently still implement __getslice__(). Therefore, you have to override it in derived classes when implementing slicing.)