Path: csiph.com!usenet.pasdenom.info!aioe.org!news.stack.nl!newsfeed.xs4all.nl!newsfeed3.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 0.002 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'else:': 0.03; 'output': 0.05; 'append': 0.09; 'logic': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'def': 0.12; 'wrote': 0.14; "'b',": 0.16; "['a',": 0.16; 'counters,': 0.16; 'itertools': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'sequence.': 0.16; 'sequential': 0.16; 'sat,': 0.16; 'basically': 0.19; 'input': 0.22; 'import': 0.22; 'skip:l 30': 0.24; 'url:home': 0.24; 'equivalent': 0.26; 'this:': 0.26; 'header:X -Complaints-To:1': 0.27; 'function': 0.29; 'wondering': 0.29; 'skip:g 30': 0.30; "i'm": 0.30; 'group:': 0.31; 'overhead': 0.31; 'subject:skip:i 10': 0.31; 'probably': 0.32; 'skip:- 30': 0.32; 'skip:# 10': 0.33; "i'd": 0.34; 'skip:u 20': 0.35; 'but': 0.35; 'there': 0.35; 'data,': 0.36; 'charset:us-ascii': 0.36; 'list': 0.37; 'list.': 0.37; 'received:76': 0.38; 'jason': 0.38; 'to:addr :python-list': 0.38; 'to:addr:python.org': 0.39; 'skip:p 20': 0.39; 'received:org': 0.40; 'new': 0.61; "'2',": 0.84; "'3',": 0.84; 'lists:': 0.91; 'wanting': 0.93; '2013': 0.98 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Dennis Lee Bieber Subject: Re: itertools.groupby Date: Sat, 20 Apr 2013 19:39:58 -0400 Organization: > Bestiaria Support Staff < References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Gmane-NNTP-Posting-Host: adsl-76-249-17-230.dsl.klmzmi.sbcglobal.net X-Newsreader: Forte Agent 3.3/32.846 X-No-Archive: YES 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: 64 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1366501207 news.xs4all.nl 2240 [2001:888:2000:d::a6]:42915 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:43973 On Sat, 20 Apr 2013 11:09:42 -0600, Jason Friedman declaimed the following in gmane.comp.python.general: > I am wanting a list of lists: > ['a', 'b', 'c'] > ['1', '2', '3', '4'] > ['X', 'Y', 'Z'] > [] > > I wrote this: > ------------------------------------ > #!/usr/bin/python3 > from itertools import groupby > > def get_lines_from_file(file_name): > with open(file_name) as reader: > for line in reader.readlines(): > yield(line.strip()) > > counter = 0 > def key_func(x): > if x.startswith("Starting a new group"): > global counter > counter += 1 > return counter > > for key, group in groupby(get_lines_from_file("my_data"), key_func): > print(list(group)[1:]) Given that the input is already grouped, in sequential terms... I'd probably avoid the whole groupby overhead since the processing is basically equivalent to a "report break". Untested/pseudo-code (I suspect this logic won't give you the empty last group...) result = [] group = None for line in fin: if line.startswith("Starting..."): if group: result.append(group) group = [] else: group.append(line) Hmmm... last group handling? if result and group == []: result.append(group) # if result we had data, and if group == [] the last input was "start a new group", so append the empty list. > I get the output I desire, but I'm wondering if there is a solution without > the global counter. No counters, no esoteric function calls... Just a straight through read/collect sequence. -- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/