Path: csiph.com!usenet.pasdenom.info!news.albasani.net!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed4.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python.list@tim.thechases.com>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.003
X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; "subject:' ": 0.07; 'cc:addr:python-list': 0.11; 'def': 0.12; '*why*': 0.16; '-tkc': 0.16; 'from:addr:python.list': 0.16; 'from:addr:tim.thechases.com': 0.16; 'from:name:tim chase': 0.16; 'inability': 0.16; 'metaclass': 0.16; 'nameerror:': 0.16; 'presume': 0.16; 'subclass': 0.16; 'subclassing': 0.16; 'subject:class': 0.16; 'tried:': 0.16; 'typeerror:': 0.16; 'wrote:': 0.18; '>>>': 0.22; 'appears': 0.22; 'import': 0.22; 'cc:addr:python.org': 0.22; 'error': 0.23; 'cc:2**0': 0.24; 'cc:no real name:2**0': 0.24; 'class.': 0.26; 'first,': 0.26; 'pass': 0.26; 'defined': 0.27; 'header:In-Reply-To:1': 0.27; 'function': 0.29; "doesn't": 0.30; "i'm": 0.30; '"",': 0.31; 'file': 0.32; 'class': 0.32; 'extend': 0.32; 'figure': 0.32; 'quite': 0.32; '(most': 0.33; 'subject:the': 0.34; "can't": 0.35; 'but': 0.35; 'acceptable': 0.36; 'doing': 0.36; 'charset:us-ascii': 0.36; 'possible': 0.36; 'hi,': 0.36; 'should': 0.36; 'error.': 0.37; 'recent': 0.39; 'sure': 0.39; 'how': 0.40; "you're": 0.61; 'name': 0.63; 'default': 0.69; 'received:50.22': 0.84
Date: Sun, 1 Dec 2013 13:43:59 -0600
From: Tim Chase <python.list@tim.thechases.com>
To: "G." <grumsk@grumsk.tz>
Subject: Re: Extending the 'function' built-in class
In-Reply-To: <529b8ba2$0$2270$426a74cc@news.free.fr>
References: <529b8ba2$0$2270$426a74cc@news.free.fr>
X-Mailer: Claws Mail 3.8.1 (GTK+ 2.24.10; x86_64-pc-linux-gnu)
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - boston.accountservergroup.com
X-AntiAbuse: Original Domain - python.org
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - tim.thechases.com
X-Get-Message-Sender-Via: boston.accountservergroup.com: authenticated_id: tim@thechases.com
Cc: python-list@python.org
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.3439.1385926961.18130.python-list@python.org>
Lines: 35
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1385926961 news.xs4all.nl 16003 [2001:888:2000:d::a6]:33908
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:60835

On 2013-12-01 19:18, G. wrote:
> Hi, I can't figure out how I can extend the 'function' built-in
> class. I tried: class test(function):
>     def test(self):
>       print("test")
> but I get an error. Is it possible ?

While I don't have an answer, I did find this interesting.  First,
"function" doesn't seem to be in the default __buitin__ namespace:

  >>> function
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  NameError: name 'function' is not defined

I presume you're doing it with the following:

  >>> from types import FunctionType
  >>> class MyFunc(FunctionType):
  ...     pass
  ... 
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
  TypeError: Error when calling the metaclass bases
      type 'function' is not an acceptable base type

but, as you mention, the inability to subclass it is somewhat
peculiar.  It appears to be metaclass-related.

I'm not quite sure *why* one might want to subclass FunctionType, but
I'm also not sure why you should be *prevented* from subclassing it.

-tkc