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Re: Reference

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Date Wed, 5 Mar 2014 23:45:25 +1100
Subject Re: Reference
From Chris Angelico <rosuav@gmail.com>
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On Wed, Mar 5, 2014 at 11:35 PM, Mark Lawrence <breamoreboy@yahoo.co.uk> wrote:
>>     if the_list is None:
>>
>>
>> Marko
>>
>
> Really great thinking, test the name the_list, which strangely enough tells
> me that this beast is a list, in the same way that THIS_IS_A_CONSTANT is a
> constant, to see if it's None.  Congratulations, you've been promoted to
> captain of my dream team.

Uhh... why? What's wrong with something either being a list or being
None to indicate no list?

def foo(x, target_list=None):
    if target_list is not None: target_list = default_targets

You can't use "if target_list:" here, because that would also catch an
empty list. You need some kind of sentinel that says "there isn't a
list here".

ChrisA

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Reference "ast" <nomail@invalid.com> - 2014-03-03 10:42 +0100
  Object identity (was: Reference) Ben Finney <ben+python@benfinney.id.au> - 2014-03-03 21:00 +1100
    Re: Object identity (was: Reference) "ast" <nomail@invalid.com> - 2014-03-03 11:21 +0100
  Re: Reference "Mark H. Harris" <harrismh777@gmail.com> - 2014-03-03 05:09 -0800
  Re: Reference Grant Edwards <invalid@invalid.invalid> - 2014-03-03 14:29 +0000
  Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-03 07:52 -0800
    Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 08:10 +1100
    Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-03 15:24 -0600
    Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 08:31 +1100
    Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-03 21:35 +0000
      Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 00:07 +0200
        Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:18 +1100
          Re: Reference Alister <alister.ware@ntlworld.com> - 2014-03-04 11:10 +0000
            Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 11:48 +0000
              Re: Reference "Rhodri James" <rhodri@wildebst.org.uk> - 2014-03-05 00:25 +0000
    Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-03 15:51 -0600
    Re: Reference Jerry Hill <malaclypse2@gmail.com> - 2014-03-03 17:02 -0500
      Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-04 00:22 +0200
        Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 09:27 +1100
        Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:33 +1100
        Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 04:52 +0000
          Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 16:24 +1100
            Re: Reference "Rhodri James" <rhodri@wildebst.org.uk> - 2014-03-05 01:08 +0000
              Re: Reference Roy Smith <roy@panix.com> - 2014-03-04 21:09 -0500
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 19:36 -0800
                Re: Reference Ian Kelly <ian.g.kelly@gmail.com> - 2014-03-04 21:08 -0700
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 20:31 -0800
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 15:32 +1100
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 20:47 -0800
                Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-05 05:06 +0000
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 21:47 -0800
                Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-05 16:01 +1000
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:10 -0800
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:22 +1100
                Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-05 16:28 +1000
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:24 +0000
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:21 +0000
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:20 +1100
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-05 09:40 -0800
                Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 12:12 -0600
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 05:33 +1100
                Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-05 18:19 +0000
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:23 +0200
                Re: Reference Grant Edwards <invalid@invalid.invalid> - 2014-03-05 20:31 +0000
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:46 +0200
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:07 +1100
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:10 +1100
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 21:34 +0000
                Re: Reference Terry Reedy <tjreedy@udel.edu> - 2014-03-05 18:00 -0500
                Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-06 03:01 +0000
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:03 -0800
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:26 +1100
                Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 17:32 +1100
                Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 08:24 -0600
                Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-05 18:29 +0000
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 22:34 +0200
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:01 +1100
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 23:14 +0200
                Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-06 08:26 +1100
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 23:50 +0200
                Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-06 00:35 +0000
                Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-06 11:50 +1100
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-06 17:46 +0000
                Re: Reference Tim Chase <python.list@tim.thechases.com> - 2014-03-05 15:33 -0600
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 08:37 +1100
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-06 02:52 +0200
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-06 12:05 +1100
                Re: Reference alex23 <wuwei23@gmail.com> - 2014-03-06 12:12 +1000
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 21:46 +0000
                Re: Reference Marko Rauhamaa <marko@pacujo.net> - 2014-03-05 08:23 +0200
                Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 22:33 -0800
                Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-05 17:40 +1100
                Re: Reference Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-03-05 12:35 +0000
                Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 23:45 +1100
          Re: Reference Jerry Hill <malaclypse2@gmail.com> - 2014-03-04 10:19 -0500
            Re: Reference Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-03-04 15:42 +0000
              Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 03:02 +1100
                Re: Reference Roy Smith <roy@panix.com> - 2014-03-04 11:14 -0500
              Re: Reference MRAB <python@mrabarnett.plus.com> - 2014-03-04 17:12 +0000
            Re: Reference Rustom Mody <rustompmody@gmail.com> - 2014-03-04 08:24 -0800
          Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 02:25 +1100
          Re: Reference Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2014-03-05 14:37 +0100
      Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 03:59 +0000
    Re: Reference Ben Finney <ben+python@benfinney.id.au> - 2014-03-04 09:17 +1100
      Re: Reference Roy Smith <roy@panix.com> - 2014-03-03 18:02 -0500
        Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-04 10:09 +1100
        Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 04:38 +0000
  Re: Reference Terry Reedy <tjreedy@udel.edu> - 2014-03-03 13:48 -0500
    Re: Reference Steven D'Aprano <steve@pearwood.info> - 2014-03-04 03:45 +0000
    Re: Reference Alexander Blinne <news@blinne.net> - 2014-03-04 13:55 +0100
      Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 01:06 +1100
        Re: Reference Alexander Blinne <news@blinne.net> - 2014-03-04 22:53 +0100
          Re: Reference Chris Angelico <rosuav@gmail.com> - 2014-03-05 09:01 +1100

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