Path: csiph.com!usenet.pasdenom.info!weretis.net!feeder1.news.weretis.net!feeder.erje.net!eu.feeder.erje.net!bcyclone03.am1.xlned.com!bcyclone03.am1.xlned.com!newsfeed.xs4all.nl!newsfeed4a.news.xs4all.nl!xs4all!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 0.003 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'subject:text': 0.05; 'context': 0.07; 'responding': 0.07; 'subject:file': 0.07; 'function,': 0.09; 'reached.': 0.09; 'python': 0.11; 'def': 0.12; 'thread': 0.14; 'ast': 0.16; 'iterator': 0.16; 'self.line': 0.16; 'thread?': 0.16; 'true:': 0.16; 'files.': 0.16; 'wrote:': 0.18; 'file,': 0.19; 'example': 0.22; 'header:User-Agent:1': 0.23; 'earlier': 0.24; 'file.': 0.24; 'least': 0.26; 'header:In-Reply- To:1': 0.27; 'raise': 0.29; 'lines': 0.31; 'subject:some': 0.31; 'file': 0.32; 'class': 0.32; 'skip:_ 10': 0.34; 'maybe': 0.34; 'message.': 0.35; 'operate': 0.35; 'but': 0.35; 'there': 0.35; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'to:addr:python.org': 0.39; 'new': 0.61; "you're": 0.61; 'you.': 0.62; 'here': 0.66; 'received:74.208': 0.68; 'to,': 0.72; 'subject:over': 0.84; 'subject:via': 0.84 Date: Fri, 28 Nov 2014 12:40:38 -0500 From: Dave Angel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: python-list@python.org Subject: Re: Iterate over text file, discarding some lines via context manager References: <5478ab81$0$2879$426a34cc@news.free.fr> In-Reply-To: <5478ab81$0$2879$426a34cc@news.free.fr> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V02:K0:VMSEv1+zKj6axZxRuywzHRE1Gk88IAAG+/EJFIBdzTK 55kyKrxm4Kayiqn9U0SMpKjbGossWeoNnGrEehtds8edgdHem2 DFl//K4vkhhcqIfdu/k3TXBag0UZgMrxQRFafZhpLQnKAusXaP Aug6eXlfGBJASiCnjpEHQUz0YVw8BKCms52XujiJPm9Bhe2f75 wbC45NSJhAKk5sI/Kinbd2WaJQxzikITbtXbRDTA2TTf/GyQPW xcJcnrfObTUvnlUghRdJQfXX1Kw1rtr3eOStw6veSKLGaTjxEI xohLcXd3c9VHRV/0Xi3+rvm4Ss6/oxCzPcLmVmom85rP0r1DPT kAUkSo/0e7u4UuuT1loc= X-UI-Out-Filterresults: notjunk:1; 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: 48 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1417196454 news.xs4all.nl 2937 [2001:888:2000:d::a6]:59062 X-Complaints-To: abuse@xs4all.nl X-Received-Bytes: 4342 X-Received-Body-CRC: 4204876086 Xref: csiph.com comp.lang.python:81697 Please don't start a new thread when responding to an existing topic. Just reply-List to the message you're responding to, and include some context from that message. On 11/28/2014 12:06 PM, ast wrote: > Hi > > Here is a solution with a custom iterator which operate on files. > I tested it with a small file. Just a remark, there are no empty line > on a file, there is at least '\n' at the end of each lines but maybe the > last one. If readline() got an emptyline, then the end of file has been > reached. > > > class MyFileItr: > def __init__(self, f): > self.f = f > self.line = "" > > def __next__(self): > > while True: > self.line = self.f.readline() > > if (self.line == ''): > raise StopIteration > if not(self.line.startswith('#') or self.line.isspace() or > self.line == '\n'): > return self.line > > def __iter__(self): > return self > > > f = open('test.txt', 'r') > > for L in MyFileItr(f): > print(L, end="") > Why would you prefer that over a generator function, as given earlier in the thread? See for example Ned's message. By using 'yield', you get Python to generate all the class boilerplate for you. -- DaveA