Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #92163

Re: Can Python function return multiple data?

Path csiph.com!usenet.pasdenom.info!news.redatomik.org!newsfeed.xs4all.nl!newsfeed1.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path <rosuav@gmail.com>
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; 'python,': 0.02; 'subject:Python': 0.05; 'elements.': 0.05; 'apis': 0.07; 'friday,': 0.07; 'pretend': 0.07; '[1,': 0.09; 'accepts': 0.09; "ain't": 0.09; 'array.': 0.09; 'immutable': 0.09; 'objects.': 0.09; 'spelled': 0.09; 'cc:addr:python-list': 0.10; 'python': 0.11; 'size,': 0.13; 'languages,': 0.15; '3],': 0.16; 'apis.': 0.16; 'count.': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'immutable,': 0.16; 'list"': 0.16; 'objects;': 0.16; 'opendir': 0.16; 'sorts': 0.16; 'url:gnu': 0.16; 'wrote:': 0.16; 'element': 0.18; 'pointer': 0.18; 'cc:2**0': 0.21; 'cc:addr:python.org': 0.21; 'pass': 0.22; '2015': 0.23; 'references': 0.23; 'header:In-Reply-To:1': 0.24; 'data,': 0.27; 'entries': 0.27; 'message-id:@mail.gmail.com': 0.28; 'arrays': 0.29; 'url:software': 0.29; 'array': 0.29; 'sense': 0.29; 'there.': 0.30; 'certainly': 0.31; 'fri,': 0.31; 'programmers': 0.31; 'point': 0.33; 'common': 0.33; "d'aprano": 0.33; 'lets': 0.33; 'null': 0.33; 'shorter': 0.33; 'steven': 0.33; 'subject:?': 0.34; 'received:google.com': 0.34; 'lists': 0.34; 'gives': 0.35; 'next': 0.35; 'identified': 0.35; 'lists.': 0.35; 'something': 0.35; 'really': 0.35; 'list': 0.35; "isn't": 0.35; 'but': 0.36; 'url:org': 0.36; '(and': 0.36; 'subject:: ': 0.37; 'say': 0.38; 'pm,': 0.39; 'things': 0.39; 'your': 0.60; 'more': 0.62; 'linked': 0.63; 'dont': 0.64; 'talking': 0.67; 'saw': 0.76; 'chrisa': 0.84; 'stashed': 0.84; 'utc+5:30,': 0.84; 'valid,': 0.84; 'to:none': 0.90
DKIM-Signature v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:cc :content-type; bh=o6n58Psre3bNmx/1CLYWzEIGVQAUcjDqyBvDx7fd6aE=; b=ThHFwLOCV7lH62mF2izP8R3soRst3kAZvO2R3EUEK0lzIidez210YtTczoPeSNKM59 5DYuPwqgkq+n8dQuqIOhYShZG+ABJ5gxgn3Cp2/qE2N6t1LmP2nsDHiRUyu/02tps4Q5 gPRkYYb6nb3pplFWgRz7ygD2Uv3AhaTJBY0ZxE6zUeFdrGjrT24gqNfpfEt2e627iwjn E+z9MeZKS5sW3doXp7plZjL0Giqy8vt8+I0WExtr0M0srP1OJWAeNWL8AKjBoEuq0FCO zFOcrwyIKy3tyIEP0bRrozLethitkm9GWc10EpiJn0uuECuK8JAtdHYjIohI++bpucXl w0Eg==
MIME-Version 1.0
X-Received by 10.42.154.65 with SMTP id p1mr12697737icw.26.1433541562775; Fri, 05 Jun 2015 14:59:22 -0700 (PDT)
In-Reply-To <33a2f501-5587-4fd9-91fa-7094d4f6c512@googlegroups.com>
References <3bbe49da-e989-4a8c-a8a9-75d3a786f508@googlegroups.com> <mailman.85.1433289398.13271.python-list@python.org> <mkn139$6hb$1@r01.glglgl.de> <CAPTjJmqQ339eamz7dBoKP83JA8QB5Z4R67T4anzgy+ZrhiscDg@mail.gmail.com> <mailman.133.1433368610.13271.python-list@python.org> <e43a00ed-2b7d-497c-aa95-e30cbc04c04a@googlegroups.com> <557056f9$0$13009$c3e8da3$5496439d@news.astraweb.com> <mailman.168.1433438784.13271.python-list@python.org> <5570ce43$0$12991$c3e8da3$5496439d@news.astraweb.com> <mailman.181.1433458775.13271.python-list@python.org> <55710b69$0$12980$c3e8da3$5496439d@news.astraweb.com> <6c78b294-efd6-4096-a572-1841aa71a5eb@googlegroups.com> <557182af$0$13014$c3e8da3$5496439d@news.astraweb.com> <33a2f501-5587-4fd9-91fa-7094d4f6c512@googlegroups.com>
Date Sat, 6 Jun 2015 07:59:22 +1000
Subject Re: Can Python function return multiple data?
From Chris Angelico <rosuav@gmail.com>
Cc "python-list@python.org" <python-list@python.org>
Content-Type text/plain; charset=UTF-8
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.20+
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.207.1433541572.13271.python-list@python.org> (permalink)
Lines 62
NNTP-Posting-Host 2001:888:2000:d::a6
X-Trace 1433541572 news.xs4all.nl 2932 [2001:888:2000:d::a6]:44876
X-Complaints-To abuse@xs4all.nl
Xref csiph.com comp.lang.python:92163

Show key headers only | View raw

On Fri, Jun 5, 2015 at 11:29 PM, Rustom Mody <rustompmody@gmail.com> wrote:
> On Friday, June 5, 2015 at 4:36:35 PM UTC+5:30, Steven D'Aprano wrote:
>> On Fri, 5 Jun 2015 01:16 pm, Rustom Mody wrote:
>> > The abstract platonic immutable list is non-existent in python
>>
>> Just pretend that "immutable list" is spelled "tuple".
>
> Ok lets say I make no fuss about the need to 'pretend'.
>
> And I try...
>
>>>> a=[1,2,3]
>>>> b=(a,a)
>>>> a
> [1, 2, 3]
>>>> b
> ([1, 2, 3], [1, 2, 3])
>>>> a.append(4)
>>>> b
> ([1, 2, 3, 4], [1, 2, 3, 4])

Congrats! You just proved that an object can itself be immutable, but
can contain references to mutables. Ain't that awesome?

Did you have a point?

> It was an analogy.
> C programmers use lists all right all the time.
> However until they see something like python, they dont know that they never
> REALLY saw lists. ie lists in python are more first-class than C.

If you're talking about the things C programmers use all the time,
they're not linked lists, they're arrays - identified by base pointer
and element count. Linked lists are common in LISPy languages, but not
all that common in C, nor C-derived APIs. Most APIs designed for C
usage are either array-based or generator-based.

http://www.gnu.org/software/libc/manual/html_node/Scanning-Directory-Content.html
Array-based: scandir accepts a pointer-to-pointer, which it populates
with a pointer to freshly-allocated data, and it returns the number of
entries stashed there.

http://www.gnu.org/software/libc/manual/html_node/Opening-a-Directory.html
http://www.gnu.org/software/libc/manual/html_node/Reading_002fClosing-Directory.html
Generator-based: opendir returns a generator, readdir gives the next
result or NULL

http://www.gnu.org/software/libc/manual/html_node/Array-Sort-Function.html
Array-based: pass it a base pointer and a count (and an object size,
since it's completely generic), and it sorts the elements.

Your point is still broadly valid, though; these arrays are not
first-class objects. They do have their own little quirks; so long as
the original array isn't deallocated, you can efficiently work with
views by simply using a base pointer inside the original array and a
length that's shorter than the whole array. Very convenient if you
need it, but most certainly not first-class lists, and can cause
problems if you're not careful. Python lists truly are first-class
objects; "more first-class than C" in the sense that 1 is more true
than 0.

ChrisA

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

Can Python function return multiple data? fl <rxjwg98@gmail.com> - 2015-06-02 14:27 -0700
  Re: Can Python function return multiple data? Joel Goldstick <joel.goldstick@gmail.com> - 2015-06-02 17:35 -0400
  Re: Can Python function return multiple data? sohcahtoa82@gmail.com - 2015-06-02 14:40 -0700
  Re: Can Python function return multiple data? John Gordon <gordon@panix.com> - 2015-06-02 21:40 +0000
  Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-03 09:56 +1000
    Re: Can Python function return multiple data? Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2015-06-03 15:56 +0200
      Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-04 07:35 +1000
      Re: Can Python function return multiple data? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-03 22:56 +0100
        Re: Can Python function return multiple data? sohcahtoa82@gmail.com - 2015-06-03 15:28 -0700
          Re: Can Python function return multiple data? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-06-03 21:30 -0400
          Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-04 11:52 +1000
          Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-04 23:47 +1000
            Re: Can Python function return multiple data? Marko Rauhamaa <marko@pacujo.net> - 2015-06-04 17:25 +0300
              Re: Can Python function return multiple data? Grant Edwards <invalid@invalid.invalid> - 2015-06-04 14:37 +0000
                Re: Can Python function return multiple data? Marko Rauhamaa <marko@pacujo.net> - 2015-06-04 18:04 +0300
                Re: Can Python function return multiple data? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-06-04 19:51 -0400
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 03:11 +1000
                Re: Can Python function return multiple data? Marko Rauhamaa <marko@pacujo.net> - 2015-06-04 20:30 +0300
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 08:37 +1000
                Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-04 13:30 -0400
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 08:31 +1000
                Re: Can Python function return multiple data? Grant Edwards <invalid@invalid.invalid> - 2015-06-04 18:38 +0000
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 08:52 +1000
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-05 09:04 +1000
                Re: Can Python function return multiple data? Grant Edwards <invalid@invalid.invalid> - 2015-06-05 02:02 +0000
                Re: Can Python function return multiple data? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-05 09:11 +0200
                Re: Can Python function return multiple data? Marko Rauhamaa <marko@pacujo.net> - 2015-06-05 12:27 +0300
                Re: Can Python function return multiple data? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-05 14:04 +0200
                Re: Can Python function return multiple data? BartC <bc@freeuk.com> - 2015-06-04 21:52 +0100
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 09:13 +1000
                Re: Can Python function return multiple data? BartC <bc@freeuk.com> - 2015-06-05 01:16 +0100
                Re: Can Python function return multiple data? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-05 02:40 +0100
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 11:48 +1000
                Re: Can Python function return multiple data? BartC <bc@freeuk.com> - 2015-06-05 11:06 +0100
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-05 07:44 +1000
                Re: Can Python function return multiple data? BartC <bc@freeuk.com> - 2015-06-05 10:51 +0100
            Re: Can Python function return multiple data? ElChino <elchino@cnn.cn> - 2015-06-04 17:37 +0200
              Re: Can Python function return multiple data? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-06-04 19:57 -0400
            Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-04 13:26 -0400
              Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 08:16 +1000
                Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-04 18:59 -0400
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 12:37 +1000
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-04 20:16 -0700
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 21:06 +1000
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-05 06:29 -0700
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-06 07:59 +1000
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-05 20:20 -0700
                Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-05 23:28 -0400
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-05 22:28 -0700
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-06 15:43 +1000
                Lawful != Mutable (was Can Python function return multiple data?) Rustom Mody <rustompmody@gmail.com> - 2015-06-07 08:49 -0700
                Re: Lawful != Mutable (was Can Python function return multiple data?) Chris Angelico <rosuav@gmail.com> - 2015-06-08 02:07 +1000
                Re: Lawful != Mutable (was Can Python function return multiple data?) Rustom Mody <rustompmody@gmail.com> - 2015-06-07 09:20 -0700
                Re: Lawful != Mutable (was Can Python function return multiple data?) Chris Angelico <rosuav@gmail.com> - 2015-06-08 02:34 +1000
                Re: Lawful != Mutable (was Can Python function return multiple data?) Rustom Mody <rustompmody@gmail.com> - 2015-06-20 18:59 -0700
                Re: Lawful != Mutable (was Can Python function return multiple data?) Chris Angelico <rosuav@gmail.com> - 2015-06-21 12:32 +1000
                Re: Lawful != Mutable (was Can Python function return multiple data?) Rustom Mody <rustompmody@gmail.com> - 2015-06-20 19:50 -0700
                Re: Lawful != Mutable (was Can Python function return multiple data?) Laura Creighton <lac@openend.se> - 2015-06-21 11:14 +0200
                Re: Lawful != Mutable (was Can Python function return multiple data?) Ron Adam <ron3200@gmail.com> - 2015-06-21 08:55 -0400
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-07 15:51 +1000
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-06 13:49 +1000
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-06 14:50 +1000
                Re: Can Python function return multiple data? Chris Angelico <rosuav@gmail.com> - 2015-06-06 15:29 +1000
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-05 22:32 -0700
                Re: Can Python function return multiple data? Dave Farrance <df@see.replyto.invalid> - 2015-06-06 07:52 +0100
                Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-07 15:53 +1000
                Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-05 08:21 -0400
                Re: Can Python function return multiple data? Marko Rauhamaa <marko@pacujo.net> - 2015-06-05 16:37 +0300
                Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-04 19:07 -0700
            Re: Can Python function return multiple data? Michael Torrie <torriem@gmail.com> - 2015-06-04 11:36 -0600
            Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-04 13:51 -0400
            Re: Can Python function return multiple data? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-04 20:17 +0200
              Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-05 08:45 +1000
                Re: Can Python function return multiple data? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2015-06-05 08:59 +0200
          Re: Can Python function return multiple data? Michael Torrie <torriem@gmail.com> - 2015-06-04 08:16 -0600
        Re: Can Python function return multiple data? sohcahtoa82@gmail.com - 2015-06-05 11:55 -0700
      Re: Can Python function return multiple data? random832@fastmail.us - 2015-06-04 01:01 -0400
      Re: Can Python function return multiple data? Ian Kelly <ian.g.kelly@gmail.com> - 2015-06-04 12:34 -0600
      Re: Can Python function return multiple data? Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-06-04 20:16 +0100
  Re: Can Python function return multiple data? Serhiy Storchaka <storchaka@gmail.com> - 2015-06-04 09:56 +0300
  Re: Can Python function return multiple data? fl <rxjwg98@gmail.com> - 2015-06-06 10:57 -0700
    Re: Can Python function return multiple data? Rustom Mody <rustompmody@gmail.com> - 2015-06-06 21:35 -0700
    Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-07 15:47 +1000
  Re: Can Python function return multiple data? Steven D'Aprano <steve@pearwood.info> - 2015-06-07 15:33 +1000

csiph-web