Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!newsfeed.fsmpi.rwth-aachen.de!rt.uk.eu.org!newsfeed.xs4all.nl!newsfeed3.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path: <python-python-list@m.gmane.org>
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; 'output': 0.05; "subject:' ": 0.07; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'python': 0.11; 'def': 0.12; 'jan': 0.12; 'expected,': 0.16; 'garbage': 0.16; 'received:80.91.229.3': 0.16; 'received:plane.gmane.org': 0.16; 'reedy': 0.16; 'subject:break': 0.16; 'subject:generator': 0.16; 'subject:when': 0.16; 'terminate.': 0.16; 'wrote:': 0.18; 'value.': 0.19; 'header:User-Agent:1': 0.23; 'header:X-Complaints- To:1': 0.27; 'header:In-Reply-To:1': 0.27; 'am,': 0.29; 'add': 0.35; 'there': 0.35; 'yield': 0.36; 'done': 0.36; 'next': 0.36; 'subject:?': 0.36; 'to:addr:python-list': 0.38; 'does': 0.39; 'received:71': 0.39; 'to:addr:python.org': 0.39; 'received:org': 0.40; 'even': 0.60; 'then,': 0.60; 'break': 0.61; 'simple': 0.61; 'here': 0.66; 'frank': 0.68; 'received:fios.verizon.net': 0.84; 'subject:you': 0.87
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: What happens when you 'break' a generator?
Date: Tue, 29 Jul 2014 03:51:05 -0400
References: <lr7hsg$3pp$1@ger.gmane.org>
Mime-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
X-Gmane-NNTP-Posting-Host: pool-71-175-90-87.phlapa.fios.verizon.net
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0
In-Reply-To: <lr7hsg$3pp$1@ger.gmane.org>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <https://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list/>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <https://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.12411.1406620291.18130.python-list@python.org>
Lines: 54
NNTP-Posting-Host: 2001:888:2000:d::a6
X-Trace: 1406620291 news.xs4all.nl 2905 [2001:888:2000:d::a6]:46079
X-Complaints-To: abuse@xs4all.nl
Xref: csiph.com comp.lang.python:75345

On 7/29/2014 3:18 AM, Frank Millman wrote:
> Hi all
>
> Python 3.4.1
>
> Here is a simple generator -
>
> def test():
>      print('start')
>      for i in range(5):
>          yield i
>      print('done')
>
> x = test()
> for j in x:
>      print(j)
>
> As expected, the output is -
>
> start
> 0
> 1
> 2
> 3
> 4
> done
>
> Here I break the loop -
>
> x = test()
> for j in x:
>      print(j)
>      if j == 2:
>          break
>
> Now the output is -
>
> start
> 0
> 1
> 2
>
> 'done' does not appear, so the generator does not actually terminate. What
> happens to it?

It sits there waiting for you to ask for the next value. Add
for j in x: print(j)
to exhaust it.  Even then, it sits there until garbage collected.



-- 
Terry Jan Reedy