1 files changed, 14 insertions, 4 deletions
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index f489535..c5ba2eb 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -87,10 +87,15 @@ loops that truncate the stream.
 
 .. function:: accumulate(iterable[, func])
 
-    Make an iterator that returns accumulated sums. Elements may be any addable
-    type including :class:`~decimal.Decimal` or :class:`~fractions.Fraction`.
-    If the optional *func* argument is supplied, it should be a function of two
-    arguments and it will be used instead of addition.
+    Make an iterator that returns accumulated sums, or accumulated
+    results of other binary functions (specified via the optional
+    *func* argument).  If *func* is supplied, it should be a function
+    of two arguments. Elements of the input *iterable* may be any type
+    that can be accepted as arguments to *func*. (For example, with
+    the default operation of addition, elements may be any addable
+    type including :class:`~decimal.Decimal` or
+    :class:`~fractions.Fraction`.) If the input iterable is empty, the
+    output iterable will also be empty.
 
     Equivalent to::
 
@@ -657,6 +662,11 @@ which incur interpreter overhead.
        "Return function(0), function(1), ..."
        return map(function, count(start))
 
+   def tail(n, iterable):
+       "Return an iterator over the last n items"
+       # tail(3, 'ABCDEFG') --> E F G
+       return iter(collections.deque(iterable, maxlen=n))
+
    def consume(iterator, n):
        "Advance the iterator n-steps ahead. If n is none, consume entirely."
        # Use functions that consume iterators at C speed.