3 from __future__ import absolute_import
5 from itertools import izip
8 def reverse_enumerate(x):
9 """Iterate through `enumerate(x)` backwards.
11 This is a memory-efficient version of `reversed(list(enumerate(x)))`.
16 >>> a = ['a', 'b', 'c']
17 >>> it = reverse_enumerate(a)
19 <type 'itertools.izip'>
21 [(2, 'c'), (1, 'b'), (0, 'a')]
22 >>> list(reversed(list(enumerate(a))))
23 [(2, 'c'), (1, 'b'), (0, 'a')]
27 `Original implemenation`_ by Christophe Simonis.
29 .. _Original implementation:
30 http://christophe-simonis-at-tiny.blogspot.com/2008/08/python-reverse-enumerate.html
32 return izip(xrange(len(x)-1, -1, -1), reversed(x))
34 # LocalWords: itertools