Index: Doc/lib/libcollections.tex
===================================================================
--- Doc/lib/libcollections.tex	(revision 54711)
+++ Doc/lib/libcollections.tex	(working copy)
@@ -388,4 +388,24 @@
     print EmployeeRecord(*tup)
 \end{verbatim}
 
+\subsection{\function{counts} accumulator \label{counts-accumulator}}
+
+\begin{funcdesc}{counts}{iterable}
+	Returns a dict where each value in the \var{iterable} is mapped to the number of
+	times it appeared.
+	\versionadded{2.6}
+	
+	Example:
+	\begin{verbatim}
+>>> items = 'acabbacba'
+>>> item_counts = counts(items)
+>>> for item in 'abcd':
+...     print item, item_counts[item]
+...
+a 4
+b 3
+c 2
+d 0
+\end{verbatim}
+
 \end{funcdesc}
Index: Lib/collections.py
===================================================================
--- Lib/collections.py	(revision 54711)
+++ Lib/collections.py	(working copy)
@@ -49,7 +49,25 @@
 
     return type(typename, (tuple,), m)
 
+def counts(iterable):
+    """Returns a mapping from values to the number of times they appeared.
 
+    >>> items = 'acabbacba'
+    >>> item_counts = counts(items)
+    >>> for item in 'abcd':
+    ...     print item, item_counts[item]
+    ...
+    a 4
+    b 3
+    c 2
+    d 0
+    """
+    count_dict = defaultdict(int)
+    for item in iterable:
+        count_dict[item] += 1
+    return count_dict
+
+
 if __name__ == '__main__':
     # verify that instances are pickable
     from cPickle import loads, dumps
Index: Lib/test/test_collections.py
===================================================================
--- Lib/test/test_collections.py	(revision 54711)
+++ Lib/test/test_collections.py	(working copy)
@@ -1,6 +1,6 @@
 import unittest
 from test import test_support
-from collections import NamedTuple
+from collections import NamedTuple, counts
 
 class TestNamedTuple(unittest.TestCase):
 
@@ -48,9 +48,32 @@
         self.assertEqual(p.y, y)
         self.assertRaises(AttributeError, eval, 'p.z', locals())
 
+class TestCounts(unittest.TestCase):
 
+    def test_dict_equality(self):
+        tests = [
+            ([], {}),
+            ([6.5], {6.5: 1}),
+            ('abcabaacb', dict(a=4, b=3, c=2)),
+            (range(10), dict.fromkeys(range(10), 1)),
+        ]
+        for iterable, expected in tests:
+            self.assertEqual(counts(iterable), expected)
+            self.assertEqual(counts(iter(iterable)), expected)
+
+    def test_item_access(self):
+        d = counts([1, 42, 3, 1, 42, 42])
+        self.assertEqual(d[0], 0)
+        self.assertEqual(d[1], 2)
+        self.assertEqual(d[2], 0)
+        d['foo'] += 1
+        self.assertEqual(d['foo'], 1)
+        d['foo'] += 2
+        self.assertEqual(d['foo'], 3)
+
+
 def test_main(verbose=None):
-    test_classes = [TestNamedTuple]
+    test_classes = [TestNamedTuple, TestCounts]
     test_support.run_unittest(*test_classes)
 
 if __name__ == "__main__":