Added hooke.util.itertools with reverse_enumerate

diff --git a/hooke/util/itertools.py b/hooke/util/itertools.py
new file mode 100644 (file)
index 0000000..5d12aa4
--- /dev/null
+++ b/hooke/util/itertools.py
@@ -0,0 +1,34 @@
+# Copyright
+
+from __future__ import absolute_import
+
+from itertools import izip
+
+
+def reverse_enumerate(x):
+    """Iterate through `enumerate(x)` backwards.
+
+    This is a memory-efficient version of `reversed(list(enumerate(x)))`.
+    
+
+    Examples
+    --------
+    >>> a = ['a', 'b', 'c']
+    >>> it = reverse_enumerate(a)
+    >>> type(it)
+    <type 'itertools.izip'>
+    >>> list(it)
+    [(2, 'c'), (1, 'b'), (0, 'a')]
+    >>> list(reversed(list(enumerate(a))))
+    [(2, 'c'), (1, 'b'), (0, 'a')]
+
+    Notes
+    -----
+    `Original implemenation`_ by Christophe Simonis.
+
+    .. _Original implementation:
+      http://christophe-simonis-at-tiny.blogspot.com/2008/08/python-reverse-enumerate.html
+    """
+    return izip(xrange(len(x)-1, -1, -1), reversed(x))
+
+#  LocalWords:  itertools