Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!news.albasani.net!feeder.news-service.com!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!194.109.133.85.MISMATCH!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.002 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'method,': 0.07; 'sep': 0.07; 'python': 0.07; 'foo': 0.09; 'api': 0.11; '>>>': 0.12; 'def': 0.13; '"copyright",': 0.16; '"credits"': 0.16; '"license"': 0.16; '(yes': 0.16; '[gcc': 0.16; 'callable,': 0.16; 'ceval.c.': 0.16; 'from:addr:kb1pkl': 0.16; 'from:name:corey richardson': 0.16; 'linux2': 0.16; 'message-id:@aim.com': 0.16; 'richardson': 0.16; 'appear': 0.19; '(which': 0.21; 'skip:{ 10': 0.23; 'objects': 0.24; 'memory': 0.24; 'version': 0.25; 'class': 0.29; "python's": 0.29; 'implement': 0.30; 'does': 0.31; 'anyone': 0.31; 'to:addr:python-list': 0.32; "i've": 0.33; 'received:192': 0.34; 'received:192.168.0': 0.35; 'print': 0.35; 'header:User-Agent:1': 0.35; 'enough': 0.37; 'else': 0.37; 'received:192.168': 0.37; 'playing': 0.38; 'but': 0.38; 'happens': 0.38; 'speak': 0.39; 'ok,': 0.39; 'to:addr:python.org': 0.39; 'could': 0.39; 'subject: (': 0.39; 'stopped': 0.40; 'would': 0.40; 'subject:The': 0.69; '__call__': 0.84; 'ate': 0.84; 'received:172.29.41': 0.84 Date: Fri, 01 Apr 2011 11:07:15 -0400 From: Corey Richardson User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.14) Gecko/20110223 Thunderbird/3.1.8 MIME-Version: 1.0 To: python-list@python.org Subject: The Magick of __call__ (Or, Digging Deeper Than I Ought To) Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit x-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:408434432:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d29444d95ea250d5b X-AOL-IP: 71.181.115.87 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Newsgroups: comp.lang.python Message-ID: Lines: 42 NNTP-Posting-Host: 82.94.164.166 X-Trace: 1301670453 news.xs4all.nl 41103 [::ffff:82.94.164.166]:57226 X-Complaints-To: abuse@xs4all.nl Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:2360 All callables (things you can foo(bar)) are really just objects that implement the __call__ method, as far as I understand. Well then, that would appear to make methods themselves callable, so let's do a little playing around... lavos@lavos ~ $ python Python 2.6.6 (r266:84292, Sep 15 2010, 16:22:56) [GCC 4.4.5] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> class Foo(object): ... def __call__(self, foo): ... self.name(foo) ... def name(self, bar): ... print "Name: {0}".format(bar) ... >>> foo = Foo() >>> foo("Me!") Name: Me! Ok, nothing out of the ordinary. But what happens if.... >>> foo.name.__call__("Corey") Name: Corey >>> eval("foo.name" + (".__call__" * 9001) + "('Corey')") Name: Corey >>> foo.name.__call__.__call__.__call__.__call__.__call__("Corey") Name: Corey >>> eval("foo.name" + (".__call__" * 100000000) + "('Corey')") ^C^Z [1]+ Stopped python (Which was then followed by a ps aux and a kill -9...it ate all my memory and then moved on to my swap.) I've been told that much magick lies in the CALL_FUNCTION bytecode, and that if I really cared I could look at ceval.c. I don't speak enough C or know enough of Python's C API for it to be of any use (yes I looked!). Would looking at something such as PyPy's version of it be good for me / does anyone else have insights? -- Corey Richardson