Path: csiph.com!news.swapon.de!fu-berlin.de!uni-berlin.de!not-for-mail From: Peter Otten <__peter__@web.de> Newsgroups: comp.lang.python Subject: Re: Why doesn't this method have access to its "self" argument? Date: Thu, 19 Nov 2015 19:00:15 +0100 Organization: None Lines: 36 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit X-Trace: news.uni-berlin.de QxFWmRVn2R0cKploIwOAMw7sJ/BEHlvuYeqIE/nCw29g== Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'elegant': 0.07; 'wrapper': 0.07; 'instance.': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:Why': 0.09; 'subject:method': 0.09; 'python': 0.10; 'def': 0.13; 'a()': 0.16; 'a(object):': 0.16; 'argument.': 0.16; 'descriptors.': 0.16; 'example)': 0.16; 'invokes': 0.16; 'received:80.91.229.3': 0.16; 'received:dip0.t-ipconnect.de': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'received:t-ipconnect.de': 0.16; 'subject:access': 0.16; 'value:': 0.16; 'wrote:': 0.16; 'attribute': 0.18; 'pointer': 0.18; 'function,': 0.22; 'pass': 0.22; 'passing': 0.23; 'written': 0.24; 'header:User-Agent:1': 0.26; "doesn't": 0.26; 'header:X -Complaints-To:1': 0.26; 'separate': 0.27; 'function': 0.28; 'seemingly': 0.29; 'workaround': 0.29; 'somebody': 0.30; "i'd": 0.31; 'maybe': 0.33; 'class': 0.33; 'instance': 0.35; 'robert': 0.35; 'but': 0.36; 'subject:" ': 0.36; 'to:addr:python-list': 0.36; 'subject:?': 0.36; 'subject:: ': 0.37; 'method': 0.37; 'received:org': 0.37; 'why': 0.39; 'to:addr:python.org': 0.40; 'received:de': 0.40; 'latest': 0.64; 'python-list': 0.66; 'receive': 0.71; 'subject:have': 0.80; 'hood': 0.84; 'subject:its': 0.84; 'subject:self': 0.84; 'subject:this': 0.85 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: p57bd8a8e.dip0.t-ipconnect.de User-Agent: KNode/4.13.3 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com comp.lang.python:99077 Robert Latest via Python-list wrote: > I found a workaround using a wrapper method which calls a C function, > passing the instance as a separate argument. It works, and I cannot see > any disadvantage. It's just not as elegant as I'd like it to be, and I > don't understand WHY the C "method" doesn't receive a pointer to the > Python instance. Maybe somebody can clarify. I don't know much about the C-implementation side, but functions written in Python are also descriptors. Given def f(self): pass class A(object): m = f c = abs v = 42 a = A() a seemingly simple attribute access m = a.m # m is now a bound method invokes f.__get__(a, A) under the hood while m = a.c assert m is abs just returns the function (abs in the example) the same way it returns any other value: v = a.v assert v == 42