Path: csiph.com!usenet.pasdenom.info!dedibox.gegeweb.org!gegeweb.eu!nntpfeed.proxad.net!proxad.net!feeder1-1.proxad.net!ecngs!feeder2.ecngs.de!newsfeed.freenet.ag!news2.euro.net!newsgate.cistron.nl!newsgate.news.xs4all.nl!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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'args': 0.04; 'paths': 0.05; 'versions.': 0.07; 'arg': 0.09; 'arguments,': 0.09; 'if,': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'terry': 0.09; 'cleanly': 0.16; 'presume': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'statement.': 0.16; 'wrote:': 0.17; 'instance,': 0.17; 'jan': 0.18; 'otherwise,': 0.20; 'earlier': 0.21; 'object.': 0.22; 'statement': 0.23; 'pass': 0.25; 'header:In-Reply-To:1': 0.25; 'header:User- Agent:1': 0.26; 'am,': 0.27; 'header:X-Complaints-To:1': 0.28; 'arguments.': 0.29; "d'aprano": 0.29; 'steven': 0.29; 'function': 0.30; 'switch': 0.32; 'to:addr:python-list': 0.33; 'skip:d 20': 0.34; 'requiring': 0.35; 'there': 0.35; 'received:org': 0.36; 'ability': 0.36; 'signature': 0.37; 'subject:: ': 0.38; 'some': 0.38; 'to:addr:python.org': 0.39; 'header:Received:5': 0.40; 'relatively': 0.62; 'provide': 0.62; 'more': 0.63; '2013': 0.84; 'received:fios.verizon.net': 0.84; 'same,': 0.91 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Terry Reedy Subject: Re: Switch statement Date: Sun, 10 Mar 2013 18:02:25 -0400 References: <513ca430$0$6512$c3e8da3$5496439d@news.astraweb.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: pool-173-75-251-66.phlapa.fios.verizon.net User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130215 Thunderbird/17.0.3 In-Reply-To: <513ca430$0$6512$c3e8da3$5496439d@news.astraweb.com> X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.15 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: 49 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1362952971 news.xs4all.nl 6926 [2001:888:2000:d::a6]:53519 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:41041 On 3/10/2013 11:18 AM, Steven D'Aprano wrote: > On Sun, 10 Mar 2013 14:16:27 +0000, Joseph L. Casale wrote: > >> I have a switch statement composed using a dict: >> >> >> switch = { >> 'a': func_a, >> 'b': func_b, >> 'c': func_c >> } >> switch.get(var, default)() >> >> >> As a result of multiple functions per choice, it migrated to: >> >> >> >> switch = { >> 'a': (func_a1, func_a2), >> 'b': (func_b1, func_b2), >> 'c': (func_c, ) >> } >> >> >> >> for f in switch.get(var, (default, )): >> f() >> >> >> As a result of only some of the functions now requiring unique >> arguments, I presume this needs to be migrated to a if/else statement? >> Is there a way to maintain the switch style with the ability in this >> scenario to cleanly pass args only to some functions? > > > The dict-as-switch-statement pattern only works when the functions all > take the same argument(s). Otherwise, you need to check which function > you are calling, and provide the right arguments. If, for instance, the functions take either 0 or 1 arg and the 1 arg is always the same, an alternative to the other suggestions is to look at the signature in an if statement. In 3.3 this is relatively ease, as inspect.signature(func) returns a signature object. There are more complicated paths in earlier versions. -- Terry Jan Reedy