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

Groups > comp.lang.python > #106817

Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask])

Path csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail
From Chris Angelico <rosuav@gmail.com>
Newsgroups comp.lang.python
Subject Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask])
Date Mon, 11 Apr 2016 10:50:36 +1000
Lines 33
Message-ID <mailman.1.1460335845.15650.python-list@python.org> (permalink)
References <neelcl$mer$1@gioia.aioe.org> <neeq6v$ruk$1@gioia.aioe.org> <1460333911.3449208.574628345.4B46CD32@webmail.messagingengine.com> <85r3ed2ctn.fsf_-_@benfinney.id.au> <CAPTjJmqXpXvDCJWPypvZodBbJ+hkf_Hizz9Cb-2-4MbLdv=-cQ@mail.gmail.com>
Mime-Version 1.0
Content-Type text/plain; charset=UTF-8
X-Trace news.uni-berlin.de efFMX23yxKJ3GlLWfZB04gUziu4v89SGmaL37vV9hsDA==
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; 'works.': 0.07; 'subject:question': 0.08; 'cc:addr:python-list': 0.09; '(1,': 0.09; 'literal': 0.09; 'optional': 0.09; 'subject:create': 0.09; 'subject:still': 0.09; 'surrounded': 0.09; 'tuple': 0.09; 'tuple.': 0.09; 'assume': 0.11; 'syntax': 0.13; 'subject: \n ': 0.15; '10:45': 0.16; '2016': 0.16; 'comma': 0.16; 'from:addr:rosuav': 0.16; 'from:name:chris angelico': 0.16; 'one- element': 0.16; 'progression': 0.16; 'received:io': 0.16; 'received:psf.io': 0.16; 'subject:Was': 0.16; 'tuple,': 0.16; 'wrote:': 0.16; 'element': 0.18; 'cc:2**0': 0.20; 'cc:addr:python.org': 0.20; '(the': 0.22; 'am,': 0.23; 'slightly': 0.23; 'this:': 0.23; 'header:In-Reply-To:1': 0.24; 'mon,': 0.24; 'followed': 0.27; 'message-id:@mail.gmail.com': 0.27; 'subject: [': 0.29; 'code:': 0.29; 'rules': 0.31; 'up.': 0.32; 'problem': 0.33; 'usually': 0.33; 'case,': 0.34; 'correctly': 0.34; 'except': 0.34; 'received:google.com': 0.35; 'but': 0.36; 'should': 0.36; 'there': 0.36; 'received:209.85': 0.36; 'basic': 0.36; 'subject:: ': 0.37; 'received:209.85.213': 0.37; 'wanted': 0.37; 'received:209': 0.38; '(1)': 0.38; 'wrong': 0.38; 'someone': 0.38; 'subject:-': 0.39; 'where': 0.40; 'some': 0.40; "you'll": 0.61; 'show': 0.62; 'different': 0.63; "they're": 0.66; 'chrisa': 0.84; 'progression.': 0.84; 'to:none': 0.91; 'subject:want': 0.93; 'examine': 0.95
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; bh=Ou/bbF2h3xg26ouYkh+aDGeyrrJ3x2LE1kjXKfyf4ac=; b=XEe9LMBrZC2sjPjLt5s9Ptlf366S5KpBexQW77KXPPb/EYGbgjbZo7npxvi+aXxxV1 ZhSPUCW6P6Q7JnktiOdjapaHWfpSV/hyWXlEf2vKwStkiscp/TaPQdzmMdFA/pRodPmS uspYkn0za6wZoqAP3JgBBJZygHQje17cDYpo6tmxzxBp1vxgZ8Zv+gGAfZAXGDTmdLxJ si2iQU6OJC0vMnJFXdKpTNLGijBk2P9HRgZV5BK9VawAw7K6jis66yeAxA877Nf62LG2 fMWnPlfkWROtJhCYCYuAiog9FncPFA07XmlSD5OOjNrHOEKgU19UWyBqhs4LPwBE2kol 0bvg==
X-Google-DKIM-Signature v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:cc; bh=Ou/bbF2h3xg26ouYkh+aDGeyrrJ3x2LE1kjXKfyf4ac=; b=iLjBXcX1YY4GSQ5Gq4OtpK0KPHj8HHmuu4rLrXdc52ptnANSXU+I16qjaVjoaqV1GL d7d/lUUgJWNkGS1V8NloO7GDMCmdOfDD1I1ebvC5cz5JFl3AONH3b/y1Etwl0gMj8wY6 p/4pmB65ig8QL9YJdt+lJWRre8EMN3rmUEw/+HZGFZPk0HgMD0FlDfw3VLMFjdYMG9Dv UlwZAvYkw3wcQ4IVVGUcTUlrkcd4QzFoWPMDSaJQf7jtEphzMZ4cJqQWaL6OarwCtYYZ aGkxs9sBVrB+pkF3kjDqSxJLnXsYcqcL2mFqSZAdW1kqszX2jeaZ09kVxHtc2J832R7P Cvug==
X-Gm-Message-State AD7BkJJagVYOFZCiCipzWBGtgxb3ehBRoS1/3y9XEhctR3qO0LboH5lccVqLuFUoiWTQxIkHnBqhOP1aR5DLQA==
X-Received by 10.50.23.80 with SMTP id k16mr15923905igf.94.1460335836916; Sun, 10 Apr 2016 17:50:36 -0700 (PDT)
In-Reply-To <85r3ed2ctn.fsf_-_@benfinney.id.au>
X-BeenThere python-list@python.org
X-Mailman-Version 2.1.21
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 <CAPTjJmqXpXvDCJWPypvZodBbJ+hkf_Hizz9Cb-2-4MbLdv=-cQ@mail.gmail.com>
X-Mailman-Original-References <neelcl$mer$1@gioia.aioe.org> <neeq6v$ruk$1@gioia.aioe.org> <1460333911.3449208.574628345.4B46CD32@webmail.messagingengine.com> <85r3ed2ctn.fsf_-_@benfinney.id.au>
Xref csiph.com comp.lang.python:106817

Show key headers only | View raw

On Mon, Apr 11, 2016 at 10:45 AM, Ben Finney <ben+python@benfinney.id.au> wrote:
> So the expanation that remains true when you examine it is: People
> wanted a literal syntax to create a zero-length tuple. A pair of parens
> is that literal syntax, and it's the parens that create the (empty)
> tuple.

But parens do NOT create a one-element tuple, and that's usually where
people trip up. If you show someone this line of code:

x = ()

and ask what x will be, you might get some wrong responses, but you'll
get a lot of people correctly deducing that it's a tuple. The problem
is that people see this progression:

x = ()
y = (1)
z = (1, 2)

and assume they're all tuples. A better progression is this:

x = ()
y = (1,)
z = (1, 2,)

where every element is followed by a comma and every tuple is
surrounded by parentheses. In that situation, everything works. There
are slightly different rules about which parts are optional (the
parens everywhere except the first case, and the last comma everywhere
except the second), but this should be the basic form of tuple
progression.

ChrisA

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

Thread

Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 18:51 -0400
  Re: Most probably a stupid question, but I still want to ask Chris Angelico <rosuav@gmail.com> - 2016-04-11 08:58 +1000
  Re: Most probably a stupid question, but I still want to ask Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 09:04 +1000
  Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 16:30 -0700
    Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:17 -0400
      Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:32 -0700
      Re: Most probably a stupid question, but I still want to ask Terry Reedy <tjreedy@udel.edu> - 2016-04-10 21:45 -0400
        Re: Most probably a stupid question, but I still want to ask Marko Rauhamaa <marko@pacujo.net> - 2016-04-11 08:41 +0300
  one-element tuples [Was: Most probably a stupid question, but I still want to ask] Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:13 -0400
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:19 -0700
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:18 -0700
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:20 +1000
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:22 -0400
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Stephen Hansen <me+python@ixokai.io> - 2016-04-10 17:28 -0700
      Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:31 +1000
        Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 20:48 -0400
          Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:56 +1000
            Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:10 +0000
              Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 10:11 -0400
                Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:26 +0000
          Re: one-element tuples Ned Batchelder <ned@nedbatchelder.com> - 2016-04-10 18:00 -0700
          Re: one-element tuples Stephen Hansen <me+python@ixokai.io> - 2016-04-10 18:07 -0700
          Re: one-element tuples "Martin A. Brown" <martin@linux-ip.net> - 2016-04-10 18:08 -0700
            Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 23:19 -0400
              Re: one-element tuples Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-04-11 09:57 +0300
              Re: one-element tuples Larry Hudson <orgnut@yahoo.com> - 2016-04-11 23:01 -0700
          Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 11:36 +1000
            Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 22:57 -0400
              Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 14:10 +1000
                Re: one-element tuples Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 00:43 -0400
                Re: one-element tuples Stephen Hansen <me+python@ixokai.io> - 2016-04-10 21:54 -0700
                Re: one-element tuples Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 15:40 +1000
                Re: one-element tuples Rustom Mody <rustompmody@gmail.com> - 2016-04-10 22:07 -0700
          Re: one-element tuples BartC <bc@freeuk.com> - 2016-04-11 12:15 +0100
            Re: one-element tuples Marko Rauhamaa <marko@pacujo.net> - 2016-04-11 15:12 +0300
              Re: one-element tuples Grant Edwards <invalid@invalid.invalid> - 2016-04-11 14:12 +0000
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:30 +1000
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] MRAB <python@mrabarnett.plus.com> - 2016-04-11 01:33 +0100
      Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Dan Sommers <dan@tombstonezero.net> - 2016-04-11 02:22 +0000
        Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 12:34 +1000
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:38 +1000
    Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:45 +1000
    Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Chris Angelico <rosuav@gmail.com> - 2016-04-11 10:50 +1000
    Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 10:57 +1000
    Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 11:04 +1000
    Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Stephen Hansen <me@ixokai.io> - 2016-04-10 18:03 -0700
    Re: Parens do create a tuple (was: one-element tuples [Was: Most probably a stupid question, but I still want to ask]) Tim Chase <python.list@tim.thechases.com> - 2016-04-10 19:52 -0500
    Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 11:41 +1000
      Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 12:32 +1000
        Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-10 22:51 -0400
          Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 14:08 +1000
            Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-11 01:27 -0400
              Re: Parens do create a tuple Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-11 18:01 +1000
                Re: Parens do create a tuple Random832 <random832@fastmail.com> - 2016-04-11 09:42 -0400
        Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 13:02 +1000
        Re: Parens do create a tuple Ben Finney <ben+python@benfinney.id.au> - 2016-04-11 14:08 +1000
    Re: Parens do create a tuple Chris Angelico <rosuav@gmail.com> - 2016-04-11 11:51 +1000
      Re: Parens do create a tuple Steven D'Aprano <steve@pearwood.info> - 2016-04-11 12:57 +1000
    Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask] Tim Chase <python.list@tim.thechases.com> - 2016-04-10 19:46 -0500
  Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve@pearwood.info> - 2016-04-11 11:50 +1000
    Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-10 22:48 -0400
      Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve@pearwood.info> - 2016-04-11 13:54 +1000
        Re: Most probably a stupid question, but I still want to ask Fillmore <fillmore_remove@hotmail.com> - 2016-04-11 00:03 -0400
          Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 21:46 -0700
            Re: Most probably a stupid question, but I still want to ask Rustom Mody <rustompmody@gmail.com> - 2016-04-10 22:18 -0700
              Re: Most probably a stupid question, but I still want to ask Stephen Hansen <me+python@ixokai.io> - 2016-04-10 22:42 -0700
                Re: Most probably a stupid question, but I still want to ask Rustom Mody <rustompmody@gmail.com> - 2016-04-10 23:57 -0700
          Re: Most probably a stupid question, but I still want to ask Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2016-04-11 17:50 +1000

csiph-web