Re: Not possible to hide local variables

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From	Cecil Westerhof <Cecil@decebal.nl>
Newsgroups	comp.lang.python
Subject	Re: Not possible to hide local variables
Organization	Decebal Computing
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Date	Wed, 29 Apr 2015 08:16:01 +0200
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Op Tuesday 28 Apr 2015 09:56 CEST schreef Ethan Furman:

> 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.

Done.


> 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.

There is something to say for this way of working.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

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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