Path: csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed4a.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 0.036 X-Spam-Evidence: '*H*': 0.93; '*S*': 0.00; '16,': 0.03; 'lines,': 0.07; 'squares': 0.07; 'builtin': 0.09; 'method,': 0.09; 'def': 0.12; 'iterator': 0.16; 'squared': 0.16; 'subject:generator': 0.16; 'true:': 0.16; 'wrote:': 0.18; 'written': 0.21; 'example': 0.22; 'creating': 0.23; 'header:User-Agent:1': 0.23; 'source': 0.25; 'subject:/': 0.26; 'van': 0.27; 'header:In-Reply-To:1': 0.27; 'am,': 0.29; "i'm": 0.30; '(although': 0.31; "d'aprano": 0.31; 'steven': 0.31; 'class': 0.32; 'skip:_ 10': 0.34; 'could': 0.34; 'something': 0.35; 'but': 0.35; 'there': 0.35; 'version': 0.36; 'sequence': 0.36; 'yield': 0.36; "didn't": 0.36; 'should': 0.36; 'to:addr:python-list': 0.38; 'to:addr:python.org': 0.39; 'break': 0.61; 'numbers': 0.61; 'further': 0.61; 'first': 0.61; 'charset:windows-1252': 0.65; 'biggest': 0.67; 'received:74.208': 0.68; 'article': 0.77; 'experiment': 0.84; 'try,': 0.84; 'usage.': 0.84; 'albert': 0.91 Date: Tue, 31 Mar 2015 09:38:16 -0400 From: Dave Angel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: python-list@python.org Subject: Re: generator/coroutine terminology References: <87y4mznmj8.fsf@elektro.pacujo.net> <55062bda$0$12998$c3e8da3$5496439d@news.astraweb.com> <551a9ebe$0$2987$e4fe514c@dreader35.news.xs4all.nl> In-Reply-To: <551a9ebe$0$2987$e4fe514c@dreader35.news.xs4all.nl> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:PXMQtKliHms4/lRKSB/pnHuqqcgBWO8rr/GCZBc4xT4h53hyVE6 CXq9uwKVLMy4hUzk3LXBWPglZCdl/kaZger+yFnau6OM2VAPzhtYnewQsRAN/V0EbZIdkc8 e73HuGvpVCDxj7D80L9b27IK2o6QKcdqMxcIralr0bDJdsciXJBp7xRJl3QYgkZBwGWshZi i2fIMNr6pW90/nGdXdk2A== X-UI-Out-Filterresults: notjunk:1; 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: 62 NNTP-Posting-Host: 2001:888:2000:d::a6 X-Trace: 1427809109 news.xs4all.nl 2837 [2001:888:2000:d::a6]:38853 X-Complaints-To: abuse@xs4all.nl Xref: csiph.com comp.lang.python:88383 On 03/31/2015 09:18 AM, Albert van der Horst wrote: > In article <55062bda$0$12998$c3e8da3$5496439d@news.astraweb.com>, > Steven D'Aprano wrote: >> >> The biggest difference is syntactic. Here's an iterator which returns a >> never-ending sequence of squared numbers 1, 4, 9, 16, ... >> >> class Squares: >> def __init__(self): >> self.i = 0 >> def __next__(self): >> self.i += 1 >> return self.i**2 >> def __iter__(self): >> return self > > You should give an example of usage. As a newby I'm not up to > figuring out the specification from source for > something built of the mysterious __ internal > thingies. > (I did experiment with Squares interactively. But I didn't get > further than creating a Squares object.) > He did say it was an iterator. So for a first try, write a for loop: class Squares: def __init__(self): self.i = 0 def __next__(self): self.i += 1 return self.i**2 def __iter__(self): return self for i in Squares(): print(i) if i > 50: break print("done") > >> >> >> Here's the same thing written as a generator: >> >> def squares(): >> i = 1 >> while True: >> yield i**2 >> i += 1 >> >> >> Four lines, versus eight. The iterator version has a lot of boilerplate >> (although some of it, the two-line __iter__ method, could be eliminated if >> there was a standard Iterator builtin to inherit from). >> -- DaveA