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Groups > comp.lang.python > #106877

Re: Parens do create a tuple

From Random832 <random832@fastmail.com>
Newsgroups comp.lang.python
Subject Re: Parens do create a tuple
Date 2016-04-11 09:42 -0400
Message-ID <mailman.30.1460382136.15650.python-list@python.org> (permalink)
References (12 earlier) <570b2330$0$1588$c3e8da3$5496439d@news.astraweb.com> <1460352479.2404917.574799201.61DF3CED@webmail.messagingengine.com> <mailman.21.1460352482.15650.python-list@python.org> <570b59db$0$1598$c3e8da3$5496439d@news.astraweb.com> <1460382133.3205062.575169425.0FE1EC18@webmail.messagingengine.com>

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On Mon, Apr 11, 2016, at 04:01, Steven D'Aprano wrote:
> What tuple that is passed to FunctionType.__call__?
> 
> Where is the tuple in these examples?
> 
> 
> py> from types import FunctionType
> py> FunctionType.__call__(lambda x: x+1, 23)
> 24
> py> FunctionType.__call__(lambda x, y: str(x)+str(y), 23, 42)
> '2342'
> 
> I don't see any evidence of a tuple being involved anywhere visible from 
> Python code.

The fact that it can be called with two positional arguments in your
first example, and three in your second, is itself weak evidence for
this (more evidence is needed to show that these aren't
keyword/positional arguments with defaults) - a pure python function
that behaved as FunctionType.__call__ would have to be defined with
*args and **kwargs. And, indeed...

>>> inspect.signature(FunctionType.__call__)
<Signature (self, /, *args, **kwargs)>

I am assuming that *args' use of a tuple is defined as part of the
language. If I'm mistaken and it can be any sequence, I suppose I stand
corrected.

> How do you know that there's a tuple involved? (That's not a 
> rhetorical question, I am genuinely curious.)

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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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