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Re: suggestions for functional style (singleton pattern?)

References (1 earlier) <13v4falb4odnhtvss4qdatnn16sgiv5pgd@4ax.com> <jAwIw.631640$rq4.16649@fx27.iad> <mailman.2.1425186322.29956.python-list@python.org> <md1dep$s0t$1@speranza.aioe.org> <54F488D0.2010906@gmail.com>
From Ian Kelly <ian.g.kelly@gmail.com>
Date 2015-03-02 09:51 -0700
Subject Re: suggestions for functional style (singleton pattern?)
Newsgroups comp.lang.python
Message-ID <mailman.55.1425315154.13471.python-list@python.org> (permalink)

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On Mon, Mar 2, 2015 at 8:59 AM, Michael Torrie <torriem@gmail.com> wrote:
> Now I don't know of any way of implementing class-style properties on a
> module as you can do in a class, but if that were needed you would write
> a standard class and instantiate a singleton inside the module itself
> perhaps.

This works, although I'm not sure that I would do it in real code.

>>> class PropertyModule(types.ModuleType):
...     @property
...     def parrot(self):
...         return "Norwegian Blue"
...
>>> sys.modules['parrot_sketch'] = PropertyModule('parrot_sketch')
>>> import parrot_sketch
>>> parrot_sketch.parrot
'Norwegian Blue'

Note that if the user does "from parrot_sketch import parrot", then
the property is evaluated at import time and any changes won't be
reflected in the local binding, which might cause some surprises.

Also, this isn't really a singleton any longer since the user might
just create another instance of the class, but you can hide the class
and present just the module as the API.

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Thread

suggestions for functional style (singleton pattern?) yves@zioup.com - 2015-02-28 16:12 -0700
  Re: suggestions for functional style (singleton pattern?) Michael Torrie <torriem@gmail.com> - 2015-02-28 19:19 -0700
    Re: suggestions for functional style (singleton pattern?) yves@zioup.com - 2015-02-28 21:11 -0700
      Re: suggestions for functional style (singleton pattern?) Michael Torrie <torriem@gmail.com> - 2015-02-28 22:14 -0700
  Re: suggestions for functional style (singleton pattern?) Mario Figueiredo <marfig@gmail.com> - 2015-03-01 04:45 +0100
    Re: suggestions for functional style (singleton pattern?) yves@zioup.com - 2015-02-28 21:29 -0700
      Re: suggestions for functional style (singleton pattern?) Michael Torrie <torriem@gmail.com> - 2015-02-28 22:05 -0700
        Re: suggestions for functional style (singleton pattern?) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-02 02:55 +1100
        Re: suggestions for functional style (singleton pattern?) Fabien <fabien.maussion@gmail.com> - 2015-03-02 11:19 +0100
          Re: suggestions for functional style (singleton pattern?) Mario Figueiredo <marfig@gmail.com> - 2015-03-02 11:31 +0100
          Re: suggestions for functional style (singleton pattern?) Michael Torrie <torriem@gmail.com> - 2015-03-02 08:59 -0700
          Re: suggestions for functional style (singleton pattern?) Ian Kelly <ian.g.kelly@gmail.com> - 2015-03-02 09:51 -0700
      Re: suggestions for functional style (singleton pattern?) Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-03-01 19:00 +1300
    Re: suggestions for functional style (singleton pattern?) Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-03-02 02:04 +1100
      Re: suggestions for functional style (singleton pattern?) Mario Figueiredo <marfig@gmail.com> - 2015-03-01 19:20 +0100
  Re: suggestions for functional style (singleton pattern?) Paul Rubin <no.email@nospam.invalid> - 2015-02-28 22:23 -0800

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