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Re: __init__ is the initialiser

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On Mon, Feb 3, 2014 at 10:40 AM, Roy Smith <roy@panix.com> wrote:
> I'm reasonably sure you posted this as humor, but there is some truth in
> what you said.  In the crypto/security domain, you often want to keep a
> key or cleartext around only for the time it's needed, and scrub the
> memory it was occupying as soon as it is no longer in use.
>
> I don't know how you would do that in Python.

I did, but you're right.

It's fundamentally not possible in pure Python, because there's no way
to flag a block of memory as "do not page this to disk". For what
you're talking about to be at all possible, you would need support
from the language, from the OS, and possibly from the CPU as well. I'm
sure this sort of thing exists, but if it does, it'll probably be
something that Python itself wouldn't concern itself with - you'd get
it via openssl or something.

There have been occasional times I've wanted an "explicit destruction"
feature. Rather than the facetious exception I listed above, it'd be
better to have all those references (including the original one in a,
since there's nothing special about that) turn into some kind of "null
state" - either None, or a special object that marks itself as a
destructed/destroyed (terminology debates aside) object. With custom
types, I can mark them off with a special flag, and check that all the
time; but I can't, for instance, have a dict that maps some lookup
keyword to its output file, and then destroy output files to remove
all their references from everywhere in the dict. (I have had
something along these lines, a bit more complicated than this, but not
in Python.)

But I do like the idea of an arsonist being unable to destroy a
painting because of the reference loop between its catalog number on
the back and the catalog itself.

ChrisA

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Re: __init__ is the initialiser Terry Reedy <tjreedy@udel.edu> - 2014-01-31 22:16 -0500
  Re: __init__ is the initialiser Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2014-02-01 05:23 +0000
    Re: __init__ is the initialiser Roy Smith <roy@panix.com> - 2014-02-01 00:25 -0500
      Re: __init__ is the initialiser Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2014-02-03 12:15 +1300
        Re: __init__ is the initialiser Chris Angelico <rosuav@gmail.com> - 2014-02-03 10:27 +1100
          Re: __init__ is the initialiser Roy Smith <roy@panix.com> - 2014-02-02 18:40 -0500
            Re: __init__ is the initialiser Chris Angelico <rosuav@gmail.com> - 2014-02-03 11:07 +1100
            Re: __init__ is the initialiser Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-02-02 17:24 -0800
            Re: __init__ is the initialiser Chris Angelico <rosuav@gmail.com> - 2014-02-03 12:37 +1100
            Re: __init__ is the initialiser Devin Jeanpierre <jeanpierreda@gmail.com> - 2014-02-02 17:54 -0800
            Re: __init__ is the initialiser Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-02-03 08:44 -0500
            Re: __init__ is the initialiser Nicholas Cole <nicholas.cole@gmail.com> - 2014-02-03 13:50 +0000
            Re: __init__ is the initialiser Ian Kelly <ian.g.kelly@gmail.com> - 2014-02-03 10:44 -0700
            Re: __init__ is the initialiser Chris Angelico <rosuav@gmail.com> - 2014-02-04 04:57 +1100
            Re: __init__ is the initialiser Nicholas Cole <nicholas.cole@gmail.com> - 2014-02-03 19:57 +0000
            Re: __init__ is the initialiser Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2014-02-03 19:38 -0500
        Re: __init__ is the initialiser Dave Angel <davea@davea.name> - 2014-02-02 19:35 -0500
          Re: __init__ is the initialiser Roy Smith <roy@panix.com> - 2014-02-02 19:45 -0500
            Re: __init__ is the initialiser Dave Angel <davea@davea.name> - 2014-02-02 22:14 -0500
            Re: __init__ is the initialiser Skip Montanaro <skip@pobox.com> - 2014-02-02 21:15 -0600
            Re: __init__ is the initialiser Dave Angel <davea@davea.name> - 2014-02-03 00:06 -0500
              Re: __init__ is the initialiser Roy Smith <roy@panix.com> - 2014-02-03 00:12 -0500
                Re: __init__ is the initialiser Chris Angelico <rosuav@gmail.com> - 2014-02-03 16:49 +1100
                Re: __init__ is the initialiser Ethan Furman <ethan@stoneleaf.us> - 2014-02-02 21:34 -0800
    Re: __init__ is the initialiser Rustom Mody <rustompmody@gmail.com> - 2014-01-31 21:31 -0800

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