Add a note on optimizing the itertools recipes for production.
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index a978c1a..4f82a27 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -784,3 +784,9 @@
except exception:
pass
+Note, many of the above recipes can be optimized by replacing global lookups
+with local variables defined as default values. For example, the
+*dotproduct* recipe can be written as::
+
+ def dotproduct(vec1, vec2, sum=sum, imap=imap, mul=operator.mul):
+ return sum(imap(mul, vec1, vec2))