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Re: NoneType and new instances

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Ethan Furman <ethan@stoneleaf.us> writes:

> Why is NoneType unable to produce a None instance? I realise that None
> is a singleton

That answers your question. Because None is a singleton, the job of its
type is to make sure there are no other instances.

> but so are True and False, and bool is able to handle returning them:

Well, they don't meet the definition of a singleton, because there are
two instances of ‘bool’ :-)

There may be code out there which depends on the fact that there once
was never a ‘bool’ type, or depends on the fact that bools are also
‘int’ instances, and it's been deemed not-worth-the-trouble to break
that code.

> This feels like a violation of 'Special cases aren't special enough to
> break the rules.'

In the case of ‘bool’, the rule was broken before being introduced.

-- 
 \          “Isn't it enough to see that a garden is beautiful without |
  `\      having to believe that there are fairies at the bottom of it |
_o__)                                             too?” —Douglas Adams |
Ben Finney

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NoneType and new instances Ethan Furman <ethan@stoneleaf.us> - 2011-07-28 08:39 -0700
  Re: NoneType and new instances Billy Mays <81282ed9a88799d21e77957df2d84bd6514d9af6@myhashismyemail.com> - 2011-07-28 11:34 -0400
  Re: NoneType and new instances Ben Finney <ben+python@benfinney.id.au> - 2011-07-29 07:46 +1000
    Re: NoneType and new instances Ethan Furman <ethan@stoneleaf.us> - 2011-07-28 15:26 -0700
      Re: NoneType and new instances Ben Finney <ben+python@benfinney.id.au> - 2011-07-29 09:52 +1000
  Re: NoneType and new instances Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-29 11:16 +1000
    Re: NoneType and new instances Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2011-07-30 14:50 +1200
      Re: NoneType and new instances Terry Reedy <tjreedy@udel.edu> - 2011-07-30 09:35 -0400
      Re: NoneType and new instances python@bdurham.com - 2011-07-30 11:43 -0400
  Re: NoneType and new instances "bruno.desthuilliers@gmail.com" <bruno.desthuilliers@gmail.com> - 2011-07-30 09:39 -0700
    Re: NoneType and new instances Terry Reedy <tjreedy@udel.edu> - 2011-07-30 23:34 -0400
      Re: NoneType and new instances Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-07-31 14:28 +1000

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