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; 'operator': 0.03; 'imply': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'behave': 0.16; 'deprecated,': 0.16; 'dictionaries': 0.16; 'equal.': 0.16; 'expecting': 0.16; 'finney': 0.16; 'operators.': 0.16; 'pythonic': 0.16; 'reason?': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'subject:versus': 0.16; 'then?': 0.16; 'url:whatsnew': 0.16; 'values?': 0.16; 'do.': 0.18; 'seems': 0.21; 'saying': 0.22; 'this?': 0.23; 'header:User-Agent:1': 0.23; 'comparing': 0.24; 'compare': 0.26; 'header:X-Complaints-To:1': 0.27; 'asked': 0.31; 'went': 0.31; 'comparison': 0.31; 'equality': 0.31; 'operators': 0.31; 'values.': 0.31; 'wright': 0.31; 'writes:': 0.31; 'yes.': 0.31; 'url:python': 0.33; 'there': 0.35; 'really': 0.36; 'false': 0.36; 'doing': 0.36; 'url:org': 0.36; 'should': 0.36; 'example,': 0.37; 'two': 0.37; 'ben': 0.38; 'to:addr:python-list': 0.38; 'expect': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'how': 0.40; 'most': 0.60; 'url:3': 0.61; 'different': 0.65; 'url:0': 0.67; 'between': 0.67; '8bit%:21': 0.69; 'borrow': 0.84; 'received:125': 0.84; 'victor': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: Ben Finney Subject: Re: Deep comparison of dicts - cmp() versus ==? Date: Fri, 20 Mar 2015 13:33:50 +1100 References: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Gmane-NNTP-Posting-Host: jigong.madmonks.org X-Public-Key-ID: 0xAC128405 X-Public-Key-Fingerprint: 517C F14B B2F3 98B0 CB35 4855 B8B2 4C06 AC12 8405 X-Public-Key-URL: http://www.benfinney.id.au/contact/bfinney-pubkey.asc X-Post-From: Ben Finney User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4 (gnu/linux) Cancel-Lock: sha1:PQhuxySmWV82/lMFNekt+MRBHek= X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.19 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: 52 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1426818822 news.xs4all.nl 2912 [2001:888:2000:d::a6]:55098 X-Complaints-To: abuse@xs4all.nl Path: csiph.com!usenet.pasdenom.info!bete-des-vosges.org!feed.ac-versailles.fr!nerim.net!novso.com!newsfeed.xs4all.nl!newsfeed3a.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail Xref: csiph.com comp.lang.python:87754 Victor Hooi writes: > What is the currently most Pythonic way for doing deep comparisons > between dicts? What distinction do you intend by saying “deep comparison”? As contrasted with what? > For example, say you have the following two dictionaries > > a = { > 'bob': { 'full_name': 'bob jones', 'age': 4, 'hobbies': ['hockey', 'tennis'], 'parents': { 'mother': 'mary', 'father', 'mike'}}, > 'james': { 'full_name': 'james joyce', 'age': 6, 'hobbies': [],} > } > > b = { > 'bob': { 'full_name': 'bob jones', 'age': 4, 'hobbies': ['hockey', 'tennis']}, > 'james': { 'full_name': 'james joyce', 'age': 5, 'hobbies': []} > } Those two dicts are not equal. How would your intended “deep comparison” behave for those two values? > However, this page seems to imply that cmp() is deprecated? > https://docs.python.org/3/whatsnew/3.0.html#ordering-comparisons It is, yes. > Should we just be using the equality operator ("==") instead then? E.g.: > > a == b Yes. That is a comparison that would return False for comparing the above two values. Would you expect different behaviour? > What is the reason for this? I don't really understand. ‘cmp’ is deprecated, and you can compare two dicts with the built-in operators. That's the reason; are you expecting some other reason? > Or is there a better way to do this? I don't really know what it is you want to do. What behaviour different from the built-in comparison operators do you want? -- \ “I went over to the neighbor's and asked to borrow a cup of | `\ salt. ‘What are you making?’ ‘A salt lick.’” —Steven Wright | _o__) | Ben Finney