[Patches] [ python-Patches-825814 ] Add list.sorted()

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Patches item #825814, was opened at 2003-10-17 19:34
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: Alex Martelli (aleax)
>Summary: Add list.sorted()

Initial Comment:
As discussed on py-dev, this returns a sorted copy of a
list while leaving the original intact.

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>Comment By: Raymond Hettinger (rhettinger)
Date: 2003-10-28 19:40

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Alex, can you give this patch a second review.

I did not put in additional classmethod warnings because all
plausible misunderstandings raise an error anyway.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2003-10-18 12:41

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Rationale for the change
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An inline sort is usable anywhere an expression is allowed.
 This includes important places like function call arguments
and list comprehensions:

  todo = [t for t in tasks.copysort() if due_today(t)]

  genhistory(date, events.copysort(key=incidenttime))

Spreading these out over multiple lines is an unnecessary
distractor from the problem domain, making the code harder
to understand and maintain.

Also, using copysort() eliminates a unnecessary variable
that changes state from unsorted to sorted and has a
lifetime longer than the data is actually needed. In longer
code fragments, this decreases code complexity, code length,
the number of variables, and decreases the risk of using a
variable in the wrong state which is a common source of
programming  errors.

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Comment By: Raymond Hettinger (rhettinger)
Date: 2003-10-18 01:26

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Revised the patch to avoid an unnecessary copy whenever the
underlying object is not referenced anywhere else -- this
occurs in the common use case:  for elem in
d.keys().copysort(): . . .


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