Re: Function defaults

Date	2011-04-24 10:07 -0700
From	Ken Seehart <ken@seehart.com>
Subject	Re: Function __defaults__
References	<4db3f444$0$29978$c3e8da3$5496439d@news.astraweb.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.798.1303666106.9059.python-list@python.org> (permalink)

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On 4/24/2011 2:58 AM, Steven D'Aprano wrote:
> Consider this in Python 3.1:
>
>
>>>> def f(a=42):
> ...     return a
> ...
>>>> f()
> 42
>>>> f.__defaults__ = (23,)
>>>> f()
> 23
>
>
> Is this an accident of implementation, or can I trust that changing
> function defaults in this fashion is guaranteed to work?

This is documented in python 3, so I would expect it to be stable (until 
python 4, that is)
http://docs.python.org/py3k/whatsnew/3.0.html#operators-and-special-methods
http://docs.python.org/py3k/library/inspect.html#types-and-members

The f.__defaults__ attribute was previously known as f.func_defaults (in 
python 2.x), which has been around, documented and stable for quite a while.

So it's probably just as safe as any other monkey patching technique. :)

Best of luck,
Ken

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Thread

Function __defaults__ Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-24 09:58 +0000
  Re: Function __defaults__ Terry Reedy <tjreedy@udel.edu> - 2011-04-24 12:48 -0400
  Re: Function __defaults__ Benjamin Kaplan <benjamin.kaplan@case.edu> - 2011-04-24 13:02 -0400
  Re: Function __defaults__ Daniel Kluev <dan.kluev@gmail.com> - 2011-04-25 04:18 +1100
  Re: Function __defaults__ Ken Seehart <ken@seehart.com> - 2011-04-24 10:07 -0700
    Re: Function __defaults__ Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-25 02:00 +0000
  Re: Function __defaults__ Ken Seehart <ken@seehart.com> - 2011-04-24 14:44 -0700
  Re: Function __defaults__ Daniel Kluev <dan.kluev@gmail.com> - 2011-04-25 08:47 +1100
  Re: Function __defaults__ Terry Reedy <tjreedy@udel.edu> - 2011-04-24 17:53 -0400
  Re: Function __defaults__ Ken Seehart <ken@seehart.com> - 2011-04-24 14:54 -0700
  Re: Function __defaults__ "Colin J. Williams" <cjw@ncf.ca> - 2011-04-25 07:59 -0400
  Re: Function __defaults__ Ken Seehart <ken@seehart.com> - 2011-04-25 05:30 -0700
  Re: Function __defaults__ "Colin J. Williams" <cjw@ncf.ca> - 2011-04-25 10:24 -0400

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