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 deque q = deque('',maxlen=10) for i in range(10,20):     q.append(i) 

the slice notation doesn't seem to work with deque...

Answer 1

import itertools output = list(itertools.islice(q, 3, 7)) 

For example:

>>> import collections, itertools >>> q = collections.deque(xrange(10, 20)) >>> q deque([10, 11, 12, 13, 14, 15, 16, 17, 18, 19]) >>> list(itertools.islice(q, 3, 7)) [13, 14, 15, 16] 

This should be more efficient the the other solutions posted so far. Proof?

[me@home]$ SETUP="import itertools,collections; q=collections.deque(xrange(1000000))"  [me@home]$ python -m timeit  "$SETUP" "list(itertools.islice(q, 10000, 20000))" 10 loops, best of 3: 68 msec per loop  [me@home]$ python -m timeit "$SETUP" "[q[i] for i in  xrange(10000, 20000)]" 10 loops, best of 3: 98.4 msec per loop  [me@home]$ python -m timeit "$SETUP" "list(q)[10000:20000]" 10 loops, best of 3: 107 msec per loop 

Answer 2

I would prefer this, it's shorter so easier to read:

output = list(q)[3:6+1]