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Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]

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From MRAB <python@mrabarnett.plus.com>
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Subject Re: one-element tuples [Was: Most probably a stupid question, but I still want to ask]
Date Mon, 11 Apr 2016 01:33:10 +0100
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On 2016-04-11 01:13, Fillmore wrote:
>
> Sorry guys. It was not my intention to piss off anyone...just trying to understand how the languare works
>
> I guess that the answer to my question is: there is no such thing as a one-element tuple,
> and Python will automatically convert a one-element tuple to a string... hence the
> behavior I observed is explained...
>
>   >>> a = ('hello','bonjour')
>   >>> b = ('hello')
>   >>> b
> 'hello'
>   >>> a
> ('hello', 'bonjour')
>   >>>
>
>
> Did I get this right this time?
>
Nope. :-)

A one-element tuple can be written as:

 >>> ('hello',)
('hello',)

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

For example, object are passed into a function thus:

     f(x, y)

(In reality, it's making a tuple and then passing that in.)

What if you want to pass in the tuple (1, 2) as a single argument?

     f((1, 2))

If you write this:

     f(1, 2)

it passes them in as 2 separate arguments.

Or consider this:

    f((1, 2), 3)

This has 2 arguments: the first is the tuple (1, 2) and the second is 
the int 3.

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.

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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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