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Re: Not possible to hide local variables

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Date Tue, 28 Apr 2015 00:56:09 -0700
From Ethan Furman <ethan@stoneleaf.us>
To python-list@python.org
Subject Re: Not possible to hide local variables
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On 04/28, Cecil Westerhof wrote:
> If I remember correctly you can not hide variables of a class or make
> them read-only?
> 
> I want to rewrite my moving average to python. The init is:
>     def __init__(self, length):
>         if type(length) != int:
>             raise ParameterError, 'Parameter has to be an int'
>         if n < 0:
>             raise ValueError, 'Parameter should be greater or equal 2'
>         self.length             = length
>         self.old_values         = []
>         self.current_total      = 0
> 
> But when someone changes length, old_values, or current_total that
> would wreck havoc with my class instance. What is the best way to
> handle this?

Prefix those names with a single leading underscore, which is the convention
for private variables.

This way, if some user (maybe you! ;) has a good reason to change those
values in can be done, but it is quite clear that said user is mucking about
with internals and they are on their own.

--
~Ethan~

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Thread

Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-28 09:33 +0200
  Re: Not possible to hide local variables Ethan Furman <ethan@stoneleaf.us> - 2015-04-28 00:56 -0700
    Re: Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 08:16 +0200
      Re: Not possible to hide local variables Michael Torrie <torriem@gmail.com> - 2015-04-29 21:10 -0600
  Re: Not possible to hide local variables Chris Angelico <rosuav@gmail.com> - 2015-04-28 18:06 +1000
    Re: Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 08:25 +0200
      Re: Not possible to hide local variables Chris Angelico <rosuav@gmail.com> - 2015-04-29 17:36 +1000
  Re: Not possible to hide local variables Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-28 18:37 +1000
    Re: Not possible to hide local variables Chris Angelico <rosuav@gmail.com> - 2015-04-28 18:44 +1000
    Re: Not possible to hide local variables Marko Rauhamaa <marko@pacujo.net> - 2015-04-28 12:20 +0300
    Re: Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 08:32 +0200
      Re: Not possible to hide local variables Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-04-30 14:05 +1000
        Re: Not possible to hide local variables Marko Rauhamaa <marko@pacujo.net> - 2015-04-30 08:10 +0300
          Re: Not possible to hide local variables Chris Angelico <rosuav@gmail.com> - 2015-04-30 16:01 +1000
  Re: Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-29 08:14 +0200
  Re: Not possible to hide local variables Grant Edwards <invalid@invalid.invalid> - 2015-04-29 14:16 +0000
    Re: Not possible to hide local variables Dave Angel <davea@davea.name> - 2015-04-29 22:31 -0400
    Re: Not possible to hide local variables Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2015-04-30 08:53 -0400
      Re: Not possible to hide local variables Cecil Westerhof <Cecil@decebal.nl> - 2015-04-30 16:50 +0200

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