Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed1.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; 'example:': 0.03; 'syntax': 0.04; 'argument': 0.05; '"""': 0.07; 'feature,': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'separating': 0.09; 'subject:skip:c 10': 0.09; 'wrote': 0.14; '4127:': 0.16; 'braces,': 0.16; 'brackets': 0.16; 'brackets,': 0.16; 'commas:': 0.16; 'constructor.': 0.16; 'denote': 0.16; 'dict': 0.16; 'dictionaries': 0.16; 'exist.': 0.16; 'optional': 0.16; 'pairs': 0.16; 'positional': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'skip:n 70': 0.16; 'ways:': 0.16; 'language': 0.16; 'wrote:': 0.18; 'library': 0.18; "aren't": 0.24; '15,': 0.26; 'possibly': 0.26; 'defined': 0.27; 'header:X -Complaints-To:1': 0.27; 'list:': 0.30; 'initialized': 0.31; 'class': 0.32; 'lists': 0.32; 'covered': 0.32; 'says': 0.33; 'url:python': 0.33; 'at:': 0.34; 'created': 0.35; 'but': 0.35; 'there': 0.35; 'format.': 0.36; 'keyword': 0.36; 'library.': 0.36; 'subject:?': 0.36; 'url:org': 0.36; 'should': 0.36; 'list': 0.37; 'to:addr:python-list': 0.38; 'pm,': 0.38; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'even': 0.60; 'tell': 0.60; 'new': 0.61; 'url:3': 0.61; 'within': 0.65; 'mar': 0.68; 'frank': 0.68; 'square': 0.74; '2015': 0.84; 'url:reference': 0.84 X-Injected-Via-Gmane: http://gmane.org/ To: python-list@python.org From: "Frank Millman" Subject: Re: Dict comprehensions - improvement to docs? Date: Mon, 16 Mar 2015 08:45:46 +0200 References: X-Gmane-NNTP-Posting-Host: 197.89.15.108 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.3790.4657 X-RFC2646: Format=Flowed; Original X-MimeOLE: Produced By Microsoft MimeOLE V6.00.3790.4913 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: 55 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1426488358 news.xs4all.nl 2836 [2001:888:2000:d::a6]:41794 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:87512 "Ian Kelly" wrote in message news:CALwzidnTUifj_L=DSH_8s+z0L44pxVvdpG1+pfz1Tzm=ECTLsw@mail.gmail.com... > On Sun, Mar 15, 2015 at 11:25 PM, Frank Millman > wrote: >> Hi all >> >> I like dict comprehensions, but I don't use them very often, so when I do >> I >> need to look up the format. > [...] > > Dict comprehensions aren't covered in the library reference because > they're a language feature, not a part of the standard library. The > syntax is defined at: > > https://docs.python.org/3/reference/expressions.html#dictionary-displays > This is what the library reference says about lists - """ Lists may be constructed in several ways: Using a pair of square brackets to denote the empty list: [] Using square brackets, separating items with commas: [a], [a, b, c] Using a list comprehension: [x for x in iterable] Using the type constructor: list() or list(iterable) """ This is what it says about dictionaries - """ Dictionaries can be created by placing a comma-separated list of key: value pairs within braces, for example: {'jack': 4098, 'sjoerd': 4127} or {4098: 'jack', 4127: 'sjoerd'}, or by the dict constructor. class dict(**kwarg) class dict(mapping, **kwarg) class dict(iterable, **kwarg) Return a new dictionary initialized from an optional positional argument and a possibly empty set of keyword arguments. """ If you did not know about dict comprehensions, there is nothing to tell you that they even exist. I feel that it should be mentioned. Frank