Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!feeds.phibee-telecom.net!newsfeed.xs4all.nl!newsfeed2a.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 0.000 X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'affected': 0.07; 'attribute': 0.07; 'incompatible': 0.07; '[1,': 0.09; 'from:addr:ethan': 0.09; 'from:addr:stoneleaf.us': 0.09; 'from:name:ethan furman': 0.09; 'handful': 0.09; 'message- id:@stoneleaf.us': 0.09; 'operand': 0.09; 'way:': 0.09; 'worse': 0.09; '~ethan~': 0.09; 'python': 0.11; 'behave': 0.16; 'collections': 0.16; 'counter()': 0.16; 'debugging,': 0.16; 'in- place': 0.16; 'instead:': 0.16; 'iterable': 0.16; 'maintainer': 0.16; 'operators.': 0.16; 'typeerror:': 0.16; "{'a':": 0.16; 'all.': 0.16; 'fix': 0.17; 'module': 0.19; '(the': 0.22; 'import': 0.22; '(in': 0.22; 'header:User-Agent:1': 0.23; 'error': 0.23; 'specifically': 0.29; "i'm": 0.30; 'code': 0.31; 'minor': 0.31; 'raised': 0.31; 'anyone': 0.31; 'quite': 0.32; 'anybody': 0.35; 'in:': 0.36; 'up!': 0.36; 'so,': 0.37; 'to:addr:python-list': 0.38; 'itself': 0.39; 'to:addr:python.org': 0.39; 'even': 0.60; 'most': 0.60; 'received:173': 0.61; 'background:': 0.68; 'real- world': 0.68; 'bitten': 0.84; 'type(s)': 0.84 Date: Wed, 05 Nov 2014 08:26:52 -0800 From: Ethan Furman User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121010 Thunderbird/16.0.1 MIME-Version: 1.0 To: Python Subject: Real-world use of Counter Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit 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: 43 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1415204817 news.xs4all.nl 2884 [2001:888:2000:d::a6]:39769 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:80278 I'm looking for real-world uses of collections.Counter, specifically to see if anyone has been surprised by, or had to spend extra-time debugging, issues with the in-place operators. Background: Most Python data types will cause a TypeError to be raised if unusable types are passed in: --> {'a': 0}.update(5) TypeError: 'int' object is not iterable --> [1, 2, 3].extend(3.14) TypeError: 'float' object is not iterable --> from collections import Counter --> Counter() + [1, 2, 3] TypeError: unsupported operand type(s) for +: 'Counter' and 'list' Most Counter in-place methods also behave this way: --> c /= [1, 2, 3] TypeError: unsupported operand type(s) for /=: 'Counter' and 'list' However, in the case of a handful of Counter in-place methods (+=, -=, &=, and |=), this is what happens instead: --> c = Counter() --> c += [1, 2, 3] AttributeError: 'list' object has no attribute 'items' Even worse (in my opinion) is the case of an empty Counter `and`ed with an incompatible type: --> c &= [1, 2, 3] --> No error is raised at all. In order to avoid unnecessary code churn (the fix itself is quite simple), the maintainer of the collections module wants to know if anybody has actually been affected by these inconsistencies, and if so, whether it was a minor inconvenience, or a compelling use-case. So, if this has bitten you, now is the time to speak up! :) -- ~Ethan~