Path: csiph.com!feeder.erje.net!2.eu.feeder.erje.net!newsfeed.kamp.net!newsfeed.kamp.net!fu-berlin.de!uni-berlin.de!not-for-mail From: Ben Finney Newsgroups: comp.lang.python Subject: Re: __del__: when to use it? What happens when you SystemExit/NameError wrt del? Method vs function calls. Date: Mon, 07 Mar 2016 14:42:15 +1100 Lines: 38 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: news.uni-berlin.de /msu0DqKDkh6eiRAmKD7nwPT7u63o9HOYDluqQtMtKHA== Cancel-Lock: sha1:DSn0Dy/LOKSRcrj/iA4H2QnK07E= Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.005 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'calls.': 0.07; 'method,': 0.07; 'garbage': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'example:': 0.10; 'def': 0.13; '__del__': 0.16; 'received:80.91.229.3': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'relates': 0.16; 'simple)': 0.16; 'subject:when': 0.16; 'systemexit': 0.16; 'too?': 0.16; 'circular': 0.18; 'windows': 0.20; 'class,': 0.22; 'exists.': 0.22; 'appears': 0.23; 'import': 0.24; 'header:User-Agent:1': 0.26; 'example': 0.26; 'header:X -Complaints-To:1': 0.26; 'dos': 0.27; 'function': 0.28; 'subject:/': 0.30; 'system,': 0.30; 'minimal': 0.30; 'rules': 0.31; 'skip:_ 10': 0.32; 'run': 0.33; 'point': 0.33; 'foo': 0.33; 'advice': 0.35; 'clear': 0.35; 'functions.': 0.35; 'subject:use': 0.35; 'but': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'expect': 0.37; 'method': 0.37; 'operating': 0.37; 'received:org': 0.37; 'mean': 0.38; 'to:addr:python.org': 0.40; 'mark': 0.40; 'more': 0.63; 'skip:\xe2 10': 0.70; '8bit%:46': 0.76; '_o__)': 0.84; 'coffin': 0.84; 'received:125': 0.84; 'subject:you': 0.85; "'don't": 0.91; 'canonical': 0.91; 'why?': 0.91 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: jigong.madmonks.org X-Public-Key-ID: 0xAC128405 X-Public-Key-Fingerprint: 517C F14B B2F3 98B0 CB35 4855 B8B2 4C06 AC12 8405 X-Public-Key-URL: http://www.benfinney.id.au/contact/bfinney-pubkey.asc X-Post-From: Ben Finney User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.21 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:104182 "Veek. M" writes: > 1. What are the rules for using __del__ besides: 'don't use it'. What do you mean by “rules”? If you want advice on using that method, I don't think a canonical exhaustive “rules” set exists. For example: Use ‘__del__’ to mark an object as no longer used; don't expect that to result in the object actually going away at any particular point in time. > 2. What happens when I SystemExit? __del__ and gc are not invoked when > I SystemExit and there's a circular reference - but why? So that we can have a concrete example: Can you give a (very minimal and simple) example demonstrating the behaviour, so we can run it too? > 3. > import foo > def __del__(self, foo=foo): > foo.bar() That appears to be a module-level function. It is not a method of any class, so I am not clear on how it relates to garbage collection. > 4. also, are method calls more efficient than function calls? All method calls are function calls. This is because all methods are functions. -- \ “Unix is an operating system, OS/2 is half an operating system, | `\ Windows is a shell, and DOS is a boot partition virus.” —Peter | _o__) H. Coffin | Ben Finney