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

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From Ben Finney <ben+python@benfinney.id.au>
Newsgroups comp.lang.python
Subject 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 10:45:08 +1000
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Stephen Hansen <me+python@ixokai.io> writes:

> […] parens don't make tuples, commas do.


Chris Angelico <rosuav@gmail.com> writes:

> The thing you're confused at is that it's not the parentheses that
> create a tuple. Parentheses merely group.


MRAB <python@mrabarnett.plus.com> writes:

> As has been said already, it's the comma that makes the tuple. The
> parentheses are often needed to avoid ambiguity.

This is too simplistic, and IMO it's just sowing the seed for future
confusion.

As MRAB states in the same message:

> There _is_ one exception though: (). It's the empty tuple (a 0-element
> tuple). It doesn't have a comma and the parentheses are mandatory.
> There's no other way to write it.

So, let's please stop saying “parens don't create a tuple”. They do, and
because of that I've stopped saying that false over-simplification.

A pair of tuples as an expression is literal syntax to create a tuple
with zero items.

Also, there is another obvious way to create an empty tuple: call the
‘tuple’ type directly:

    >>> foo = tuple()
    >>> print(type(foo), len(foo))
    <class 'tuple'> 0

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.

-- 
 \     “It is hard to believe that a man is telling the truth when you |
  `\      know that you would lie if you were in his place.” —Henry L. |
_o__)                                                          Mencken |
Ben Finney

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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

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