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Re: Common LISP-style closures with Python

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On Sat, 04 Feb 2012 02:27:56 +0200
Antti J Ylikoski <antti.ylikoski@tkk.fi> wrote:

[...]


> 
> # Make a Common LISP-like closure with Python.
> #
> # Antti J Ylikoski 02-03-2012.
> 
> def f1():
>      n = 0
>      def f2():
>          nonlocal n
>          n += 1
>          return n
>      return f2
>
 
[...]

> 
> i. e. we can have several functions with private local states which
> are kept between function calls, in other words we can have Common
> LISP-like closures.
> 

I'm not sure how naughty this is, but the same thing can be done without using
nonlocal by storing the local state as an attribute of the enclosed function
object:

>>> def f():
...     def g():
...             g.count += 1
...             return g.count
...     g.count = 0
...     return g
... 
>>> h = f()
>>> j = f()
>>> h()
1
>>> h()
2
>>> h()
3
>>> j()
1
>>> j()
2
>>> j()
3

This way, you can also write to the attribute:

>>> j.count = 0
>>> j()
1


John

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Thread

Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-04 02:27 +0200
  Re: Common LISP-style closures with Python Chris Rebert <clp2@rebertia.com> - 2012-02-03 18:47 -0800
    Re: Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-04 12:14 +0200
      Re: Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-04 12:23 +0200
      Re: Common LISP-style closures with Python Arnaud Delobelle <arnodel@gmail.com> - 2012-02-04 10:58 +0000
        Re: Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-04 15:09 +0200
          Re: Common LISP-style closures with Python Tomasz Rola <rtomek@ceti.pl> - 2012-02-04 18:42 +0100
      Re: Common LISP-style closures with Python Devin Jeanpierre <jeanpierreda@gmail.com> - 2012-02-04 17:52 -0500
  Re: Common LISP-style closures with Python John O'Hagan <research@johnohagan.com> - 2012-02-05 12:31 +1100
    Re: Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-05 06:19 +0200
      Re: Common LISP-style closures with Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-05 13:58 -0700
        Re: Common LISP-style closures with Python Antti J Ylikoski <antti.ylikoski@tkk.fi> - 2012-02-06 07:55 +0200
  Re: Common LISP-style closures with Python Rick Johnson <rantingrickjohnson@gmail.com> - 2012-02-05 15:29 -0800
  Re: Common LISP-style closures with Python John Nagle <nagle@animats.com> - 2012-02-09 22:26 -0800
  Re: Common LISP-style closures with Python 88888 Dihedral <dihedral88888@googlemail.com> - 2012-02-09 23:55 -0800

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