Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder4.news.weretis.net!feeder2.ecngs.de!ecngs!feeder.ecngs.de!xlned.com!feeder1.xlned.com!newsfeed.xs4all.nl!newsfeed5.news.xs4all.nl!xs4all!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 0.001 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'exception': 0.03; 'argument': 0.04; 'exception.': 0.07; 'suppose': 0.07; 'try:': 0.07; 'python': 0.09; 'defined.': 0.09; 'here?': 0.09; 'def': 0.10; 'aug': 0.13; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'integer.': 0.16; 'nan': 0.16; 'possible?': 0.16; 'subject:arithmetic': 0.16; 'wrote:': 0.17; 'thu,': 0.17; 'define': 0.20; 'received:209.85.214.174': 0.21; 'raise': 0.24; 'header:In-Reply-To:1': 0.25; 'message-id:@mail.gmail.com': 0.27; "doesn't": 0.28; 'division': 0.29; 'prints': 0.29; "i'm": 0.29; 'function': 0.30; 'could': 0.32; 'print': 0.32; 'like:': 0.33; 'point,': 0.33; 'to:addr:python-list': 0.33; 'likely': 0.33; 'received:google.com': 0.34; 'pm,': 0.35; 'received:209.85': 0.35; 'something': 0.35; 'there': 0.35; 'except': 0.36; 'but': 0.36; 'possible': 0.37; 'why': 0.37; 'passed': 0.37; 'skip:z 10': 0.37; 'received:209': 0.37; 'subject:: ': 0.38; 'mark': 0.38; 'easier': 0.38; 'sure': 0.38; 'instead': 0.39; 'to:addr:python.org': 0.39; 'received:209.85.214': 0.39; 'header:Received:5': 0.40; 'most': 0.61; '666': 0.84 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=q+EgosQmQsjs0CDE6uv/nWWd9U82e2QcbJTnbZCVfaY=; b=Db6FCw9RmtQXk8JFxGPO32e7TPN6iGwaEKbOClMZOwt7QdyQpyI3sWW9ICzf+ZqQj0 5zJ7NJ2+qoCz4k3j7ll2YM//FuyYbHs0hx+QaLsGDmgP6cN89RkJkzOxDp7Q4g54ukba yOvNQGAz2YTa9ALQKmrZgoUJkjpvmxnKc8nLBSFy9rl1Sbu58e12jtIVqhjycSGevPW5 STEZLuTnYz49GO77xfuUEecZeArbwss17kGSQCZXfBEtzUizKeCVni2irQyFTxHZvPTo X12TrMGIITiGLK7ZAURooc/uWoyh2Ihd7UdqyWlFy2SmDOmRfLVaLsvc2+0DZAuZmy/a 9NyQ== MIME-Version: 1.0 In-Reply-To: <8b9a5844-66b0-4940-946a-5e626462cdce@googlegroups.com> References: <8b9a5844-66b0-4940-946a-5e626462cdce@googlegroups.com> Date: Thu, 23 Aug 2012 19:16:08 +1000 Subject: Re: Guarding arithmetic From: Chris Angelico To: python-list@python.org Content-Type: text/plain; charset=ISO-8859-1 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: 26 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1345713371 news.xs4all.nl 6926 [2001:888:2000:d::a6]:41379 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:27711 On Thu, Aug 23, 2012 at 7:05 PM, Mark Carter wrote: > Suppose I want to define a function "safe", which returns the argument passed if there is no error, and 42 if there is one. So the setup is something like: > > def safe(x): > # WHAT WOULD DEFINE HERE? > > print safe(666) # prints 666 > print safe(1/0) # prints 42 > > I don't see how such a function could be defined. Is it possible? That can work ONLY if the division of 1/0 doesn't raise an exception. This is why the concept of NaN exists; I'm not sure if there's a way to tell Python to return NaN instead of bombing, but it's most likely only possible with floating point, not integer. However, there's an easier way. try: print 1/0 except ZeroDivisionError: print 42 Catch the exception and do with it what you will. ChrisA