Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail From: Mark Lawrence Newsgroups: comp.lang.python Subject: Re: empty clause of for loops Date: Wed, 16 Mar 2016 13:45:53 +0000 Lines: 69 Message-ID: References: <56E93413.6090108@mail.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.uni-berlin.de 50lCgcNPtZdOvjVOSG07uACyDKvZjFj07MKtwl9chLxQ== 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; 'from:addr:yahoo.co.uk': 0.05; 'none:': 0.05; 'issue:': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'def': 0.13; 'wed,': 0.15; '2016': 0.16; 'language:': 0.16; 'list)': 0.16; 'pythonic': 0.16; 'received:80.91.229.3': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'true:': 0.16; 'wrote:': 0.16; 'try:': 0.18; 'variable': 0.18; 'language': 0.19; '>>>': 0.20; 'lawrence': 0.22; 'pass': 0.22; 'header:In-Reply-To:1': 0.24; 'header:User-Agent:1': 0.26; 'header:X-Complaints-To:1': 0.26; 'yield': 0.27; 'raise': 0.29; "i'm": 0.30; 'language.': 0.32; 'class': 0.33; 'except': 0.34; 'this?': 0.34; 'false': 0.35; 'mine': 0.35; 'something': 0.35; 'item': 0.35; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'received:org': 0.37; 'doing': 0.38; 'stuff': 0.38; 'hi,': 0.38; 'test': 0.39; 'to:addr:python.org': 0.40; 'mark': 0.40; 'charset:windows-1252': 0.62; 'our': 0.64; 'mar': 0.65; '>>>>>': 0.66; 'course.': 0.67; 'otten': 0.84; 'pythonistas,': 0.84; 'colleague': 0.93 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: 80.234.129.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.0 In-Reply-To: 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:105026 On 16/03/2016 13:25, alister wrote: > On Wed, 16 Mar 2016 11:47:31 +0100, Peter Otten wrote: > >> Sven R. Kunze wrote: >> >>> Hi, >>> >>> a colleague of mine (I write this mail because I am on the list) has >>> the following issue: >>> >>> >>> for x in my_iterable: >>> # do >>> empty: >>> # do something else >>> >>> >>> What's the most Pythonic way of doing this? >> >> What would you expect? >> >>>>> class Empty(Exception): pass >> ... >>>>> def check_empty(items): >> ... items = iter(items) >> ... try: >> ... yield next(items) >> ... except StopIteration: >> ... raise Empty ... yield from items ... >>>>> try: >> ... for item in check_empty("abc"): print(item) >> ... except Empty: print("oops") >> ... >> a >> b >> c >>>>> try: >> ... for item in check_empty(""): print(item) >> ... except Empty: print("oops") >> ... >> oops >> >> I'm kidding, of course. Keep it simple and use a flag like you would in >> any other language: >> >> empty = True: >> for item in items: >> empty = False ... >> if empty: >> ... > > or even use the loop variable as the flag > > item=None > for item in items: > #do stuff > if ex is None: > #do something else > Did you test this? :) -- My fellow Pythonistas, ask not what our language can do for you, ask what you can do for our language. Mark Lawrence