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svn+ssh://pythondev@svn.python.org/python/trunk

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  r60965 | eric.smith | 2008-02-22 18:43:17 +0100 (Fri, 22 Feb 2008) | 1 line

  Tests for bin() builtin.  These need to get merged into py3k, which has no tests for bin.
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  r60968 | raymond.hettinger | 2008-02-22 20:50:06 +0100 (Fri, 22 Feb 2008) | 1 line

  Document itertools.product().
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  r60969 | raymond.hettinger | 2008-02-23 03:20:41 +0100 (Sat, 23 Feb 2008) | 9 lines

  Improve the implementation of itertools.product()

  * Fix-up issues pointed-out by Neal Norwitz.
  * Add extensive comments.
  * The lz->result variable is now a tuple instead of a list.
  * Use fast macro getitem/setitem calls so most code is in-line.
  * Re-use the result tuple if available (modify in-place instead of copy).
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  r60972 | raymond.hettinger | 2008-02-23 05:03:50 +0100 (Sat, 23 Feb 2008) | 1 line

  Add more comments
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  r60973 | raymond.hettinger | 2008-02-23 11:04:15 +0100 (Sat, 23 Feb 2008) | 1 line

  Add recipe using itertools.product().
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  r60974 | facundo.batista | 2008-02-23 13:01:13 +0100 (Sat, 23 Feb 2008) | 6 lines


  Issue 1881. Increased the stack limit from 500 to 1500. Also added
  a test for this (and because of this test you'll see in stderr a
  message that parser.c sends before raising MemoryError).
  Thanks Ralf Schmitt.
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  r60975 | facundo.batista | 2008-02-23 13:27:17 +0100 (Sat, 23 Feb 2008) | 4 lines


  Issue 1776581. Minor corrections to smtplib, and two small tests.
  Thanks Alan McIntyre.
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  r60976 | facundo.batista | 2008-02-23 13:46:10 +0100 (Sat, 23 Feb 2008) | 5 lines


  Issue 1781. Now ConfigParser.add_section does not let you add a
  DEFAULT section any more, because it duplicated sections with
  the rest of the machinery. Thanks Tim Lesher and Manuel Kaufmann.
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1 files changed, 29 insertions, 0 deletions

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 013ed38..af73b57 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -289,6 +289,29 @@ loops that truncate the stream.
    example :func:`islice` or :func:`takewhile`).
 
 
+.. 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)
+
+
 .. function:: repeat(object[, times])
 
    Make an iterator that returns *object* over and over again. Runs indefinitely
@@ -526,3 +549,9 @@ which incur interpreter overhead. ::
                pending -= 1
                nexts = cycle(islice(nexts, pending))
 
+   def powerset(iterable):
+       "powerset('ab') --> set([]), set(['b']), set(['a']), set(['a', 'b'])"
+       skip = object()
+       for t in product(*izip(repeat(skip), iterable)):
+           yield set(e for e in t if e is not skip)
+