Merged revisions 61038,61042-61045,61047,61050,61053,61055-61056,61061-61064,61066-61080 via svnmerge from

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

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  r61063 | andrew.kuchling | 2008-02-25 17:29:19 +0100 (Mon, 25 Feb 2008) | 1 line

  Move .setupterm() output so that we don't try to call endwin() if it fails
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  r61064 | andrew.kuchling | 2008-02-25 17:29:58 +0100 (Mon, 25 Feb 2008) | 1 line

  Use file descriptor for real stdout
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  r61067 | facundo.batista | 2008-02-25 19:06:00 +0100 (Mon, 25 Feb 2008) | 4 lines


  Issue 2117.  Update compiler module to handle class decorators.
  Thanks Thomas Herve
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  r61069 | georg.brandl | 2008-02-25 21:17:56 +0100 (Mon, 25 Feb 2008) | 2 lines

  Rename sphinx.addons to sphinx.ext.
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  r61071 | georg.brandl | 2008-02-25 21:20:45 +0100 (Mon, 25 Feb 2008) | 2 lines

  Revert r61029.
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  r61072 | facundo.batista | 2008-02-25 23:33:55 +0100 (Mon, 25 Feb 2008) | 4 lines


  Issue 2168. gdbm and dbm needs to be iterable; this fixes a
  failure in the shelve module.  Thanks Thomas Herve.
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  r61073 | raymond.hettinger | 2008-02-25 23:42:32 +0100 (Mon, 25 Feb 2008) | 1 line

  Make sure the itertools filter functions give the same performance for func=bool as func=None.
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  r61074 | raymond.hettinger | 2008-02-26 00:17:41 +0100 (Tue, 26 Feb 2008) | 1 line

  Revert part of r60927 which made invalid assumptions about the API offered by db modules.
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  r61075 | facundo.batista | 2008-02-26 00:46:02 +0100 (Tue, 26 Feb 2008) | 3 lines


  Coerced PyBool_Type to be able to compare it.
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  r61076 | raymond.hettinger | 2008-02-26 03:46:54 +0100 (Tue, 26 Feb 2008) | 1 line

  Docs for itertools.combinations().  Implementation in forthcoming checkin.
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  r61077 | neal.norwitz | 2008-02-26 05:50:37 +0100 (Tue, 26 Feb 2008) | 3 lines

  Don't use a hard coded port.  This test could hang/fail if the port is in use.
  Speed this test up by avoiding a sleep and using the event.
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  r61078 | neal.norwitz | 2008-02-26 06:12:50 +0100 (Tue, 26 Feb 2008) | 1 line

  Whitespace normalization
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  r61079 | neal.norwitz | 2008-02-26 06:23:51 +0100 (Tue, 26 Feb 2008) | 1 line

  Whitespace normalization
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  r61080 | georg.brandl | 2008-02-26 07:40:10 +0100 (Tue, 26 Feb 2008) | 2 lines

  Banish tab.
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1 files changed, 44 insertions, 2 deletions

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index af73b57..d04f33b 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -74,6 +74,45 @@ loops that truncate the stream.
                   yield element
 
 
+.. function:: combinations(iterable, r)
+
+   Return successive *r* length combinations of elements in the *iterable*.
+
+   Combinations are emitted in a lexicographic sort order.  So, if the 
+   input *iterable* is sorted, the combination tuples will be produced
+   in sorted order.  
+
+   Elements are treated as unique based on their position, not on their
+   value.  So if the input elements are unique, there will be no repeat
+   values within a single combination.
+
+   Each result tuple is ordered to match the input order.  So, every
+   combination is a subsequence of the input *iterable*.
+
+   Example:  ``combinations(range(4), 3) --> (0,1,2), (0,1,3), (0,2,3), (1,2,3)``
+
+   Equivalent to::
+
+        def combinations(iterable, r):
+            pool = tuple(iterable)
+            if pool:
+                n = len(pool)
+                vec = range(r)
+                yield tuple(pool[i] for i in vec)
+                while 1:
+                    for i in reversed(range(r)):
+                        if vec[i] == i + n-r:
+                            continue
+                        vec[i] += 1
+                        for j in range(i+1, r):
+                            vec[j] = vec[j-1] + 1
+                        yield tuple(pool[i] for i in vec)
+                        break
+                    else:
+                        return
+
+   .. versionadded:: 2.6
+
 .. function:: count([n])
 
    Make an iterator that returns consecutive integers starting with *n*. If not
@@ -298,9 +337,12 @@ loops that truncate the stream.
 
    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).
+   changing on every iteration).  This results in a lexicographic ordering
+   so that if the inputs iterables are sorted, the product tuples are emitted
+   in sorted order.
 
-   Equivalent to (but without building the entire result in memory)::
+   Equivalent to the following except that the actual implementation does not
+   build-up intermediate results in memory::
 
        def product(*args):
            pools = map(tuple, args)