[Python-checkins] r60968 - in python/trunk: Doc/library/itertools.rst Misc/NEWS

[raymond.hettinger]

Author: raymond.hettinger
Date: Fri Feb 22 20:50:06 2008
New Revision: 60968

Modified:
   python/trunk/Doc/library/itertools.rst
   python/trunk/Misc/NEWS
Log:
Document itertools.product().

Modified: python/trunk/Doc/library/itertools.rst
==============================================================================
--- python/trunk/Doc/library/itertools.rst	(original)
+++ python/trunk/Doc/library/itertools.rst	Fri Feb 22 20:50:06 2008
@@ -302,6 +302,29 @@
 
    .. versionadded:: 2.6
 
+.. function:: product(*iterables)
+
+   Cartesian product of input iterables.
+
+   Equivalent to nested for-loops in a generator expression. For example,
+   ``product(A, B)`` returns the same as ``((x,y) for x in A for y in B)``.
+
+   The leftmost iterators are in the outermost for-loop, so the output tuples
+   cycle in a manner similar to an odometer (with the rightmost element
+   changing on every iteration).
+
+   Equivalent to (but without building the entire result in memory)::
+
+       def product(*args):
+           pools = map(tuple, args)
+           if pools:            
+               result = [[]]
+               for pool in pools:
+                   result = [x+[y] for x in result for y in pool]
+               for prod in result:
+                   yield tuple(prod)
+
+   .. versionadded:: 2.6
 
 .. function:: repeat(object[, times])
 

Modified: python/trunk/Misc/NEWS
==============================================================================
--- python/trunk/Misc/NEWS	(original)
+++ python/trunk/Misc/NEWS	Fri Feb 22 20:50:06 2008
@@ -635,6 +635,9 @@
 - itertools.count() is no longer bounded to LONG_MAX.  Formerly, it raised
   an OverflowError.  Now, automatically shifts from ints to longs.
 
+- Added itertools.product() which forms the Cartesian product of
+  the input iterables.
+
 - Patch #1541463: optimize performance of cgi.FieldStorage operations.
 
 - Decimal is fully updated to the latest Decimal Specification (v1.66).