[Patches] [ python-Patches-823292 ] Optional list.sort() args for DSU pattern and reverse

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Patches item #823292, was opened at 2003-10-14 03:53
Message generated for change (Comment added) made by rhettinger
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Category: Core (C code)
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Raymond Hettinger (rhettinger)
Assigned to: Nobody/Anonymous (nobody)
Summary: Optional list.sort() args for DSU pattern and reverse

Initial Comment:
Here is a first draft patch as discussed on python-dev.
 Docs and tests to follow.

The keywords are:  cmpfunc, key, reverse

This patch passes regression tests and a minimal set of
basic functionality tests which need to be expanded
considerably.  I'll need to go back over this one in
more detail to check:

* Was the code inserted in the right place with respect
to the existing anti-mutation code.

* Is the strategy of decorating in-place to aggressive?
 Decoration consists of *replacing* each value x with
(x, key(x)).

* Verify reference counting and error handling.

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>Comment By: Raymond Hettinger (rhettinger)
Date: 2003-10-14 23:51

Message:
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Added a cmp function wrapper so that the key will be
unwrapped for a user specified cmp function applied to
wrapped keys.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2003-10-14 21:35

Message:
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Here is a second patch including unittests and docs.

* The optional keywords arguments are:  cmp, key, reverse.

* The key function triggers a DSU step with a wrapper object
that holds the full record, but returns only the key for a
comparision.  This is fast and doesn't change the underlying
stability characteristics of the sort. (I think this was
Neil's idea -- and it works well.)

* If the key function is not specified, no wrapping occurs
so that sort performance is not affected.



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