Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From: Grant Edwards <grant.b.edwards@gmail.com>
Newsgroups: comp.lang.python
Subject: Re: Iteration, while loop, and for loop
Date: Tue, 28 Jun 2016 17:58:52 +0000 (UTC)
Lines: 39
Message-ID: <mailman.90.1467136751.2358.python-list@python.org>
References: <079ff112-8f18-4a27-938f-12e4e55a4a5b@googlegroups.com> <577295b3$0$1598$c3e8da3$5496439d@news.astraweb.com> <20160628122308.4578d876@bigbox.christie.dr> <nkudsr$335$1@ger.gmane.org>
X-Trace: news.uni-berlin.de fu2fXlo0cd7/TGcadm1CxQCV4SjseYIGRf5kPo0d1hTw==
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 0.001
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'bytes.': 0.07; 'data:': 0.07; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'received:qwest.net': 0.09; 'subject:while': 0.09; ':-)': 0.12; 'things.': 0.15; '"for"': 0.16; '"while"': 0.16; 'iterated': 0.16; 'len': 0.16; 'loops': 0.16; 'pythonic': 0.16; 'received:80.91.229.3': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'wrote:': 0.16; 'bytes': 0.18; 'seems': 0.23; 'tim': 0.24; 'header :User-Agent:1': 0.26; 'header:X-Complaints-To:1': 0.26; 'sequence': 0.27; 'chase': 0.29; 'queue': 0.29; 'yields': 0.29; "d'aprano": 0.33; 'steven': 0.33; 'wrap': 0.33; 'similar': 0.33; 'that,': 0.34; 'something': 0.35; 'item': 0.35; 'but': 0.36; 'skip:i 20': 0.36; 'there': 0.36; 'to:addr:python-list': 0.36; 'subject:: ': 0.37; 'being': 0.37; 'received:org': 0.37; 'things': 0.38; 'data': 0.39; 'to:addr:python.org': 0.40; 'where': 0.40; 'still': 0.40; 'some': 0.40; 'your': 0.60; 'telling': 0.61; 'more': 0.63; 'great': 0.63; 'done:': 0.84; 'edwards': 0.91
X-Injected-Via-Gmane: http://gmane.org/
X-Gmane-NNTP-Posting-Host: 67-130-15-94.dia.static.qwest.net
User-Agent: slrn/1.0.2 (Linux)
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.22
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>
X-Mailman-Original-Message-ID: <nkudsr$335$1@ger.gmane.org>
X-Mailman-Original-References: <079ff112-8f18-4a27-938f-12e4e55a4a5b@googlegroups.com> <577295b3$0$1598$c3e8da3$5496439d@news.astraweb.com> <20160628122308.4578d876@bigbox.christie.dr>
Xref: csiph.com comp.lang.python:110720

On 2016-06-28, Tim Chase <python.list@tim.thechases.com> wrote:
> On 2016-06-29 01:20, Steven D'Aprano wrote:
>> While loops are great for loops where you don't know how many
>> iterations there will be but you do know that you want to keep
>> going while some condition applies:
>> 
>> while there is still work to be done:
>>     do some more work
>
> I find this particularly the case when the thing being iterated over
> can be changed, such as a queue of things to process:
>
>   items = deque()
>   items.append(root_node)
>   while items:
>     item = items.popleft()
>     process(item)
>     items.extend(item.children)

Yep, I often do something similar when processing a block of data
bytes comprising a sequence of "things" of varying number of bytes.

    data = read_a_blob_of_bytes()
    while data:
        #figure out how long the first "thing" is
        len = <some expression typically involving the first few bytes of 'data'>  
        handle_thing(data[:len])
        data = data[len:]
> But then, if you wrap up your "while" loop as a generator that yields
> things, you can then use it in a "for" loop which seems to me like
> the Pythonic way to do things. :-)

Yea, I keep telling myself that, but I never actually do it.

-- 
Grant Edwards               grant.b.edwards        Yow! How do I get HOME?
                                  at               
                              gmail.com