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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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 @@
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 @@
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)