Re: Importing variables non-deterministic?

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Date	2013-08-19 09:32 +0100
Subject	Re: Importing variables non-deterministic?
From	Chris Angelico <rosuav@gmail.com>
Newsgroups	comp.lang.python
Message-ID	<mailman.17.1376901181.19984.python-list@python.org> (permalink)

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On Mon, Aug 19, 2013 at 9:16 AM, Antoon Pardon
<antoon.pardon@rece.vub.ac.be> wrote:
> Op 19-08-13 09:45, Dave Angel schreef:
>> Antoon Pardon wrote:
>>> I think you are overstating your case. Classes and functions are
>>> variables too and in general nobody seems to have a problem with them
>>> being global.
>>>
>>
>> It's global *variables* that are to be avoided.  constants like clsases
>> and functions are fine.  On the other hand, class attributes can be
>> variable, and thus are to be avoided when reasonable.
>
> Python has no constants. Classes and functions can be changed just like
> any other variable. I agree that classes and function are generally
> meant to be constant, but often enought so are global int variables.

# telnet.py
IAC = 0xFF
GA = 0xF9
WILL = 0xFB
WONT = 0xFC
DO = 0xFD
DONT = 0xFE

# connection.py
from telnet import IAC,DO,DONT

To be sure, Python won't stop me from changing the value of DONT. But
it's a constant, and its value is defined elsewhere (RFC 854). (In
this instance, an enum would probably be the better option; but this
is an example of a more general case.)

In connection.py, I don't care that I've taken a "copy" of the integer
0xFE. It's never going to change; it is a constant in the best
tradition of "named number". I could hard-code 0xFE everywhere and the
code would work *just fine*, but it'd be less readable, so I don't.

Python does have constants. It just doesn't have interpreter support
for them. Same as private members, in fact.

ChrisA

Thread

Importing variables non-deterministic? tmellman@googlemail.com - 2013-08-17 07:25 -0700
  Re: Importing variables non-deterministic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-17 15:01 +0000
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 09:14 +0200
    Re: Importing variables non-deterministic? Dave Angel <davea@davea.name> - 2013-08-19 07:45 +0000
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 10:16 +0200
      Re: Importing variables non-deterministic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-19 16:57 +0000
        Re: Importing variables non-deterministic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-19 17:16 +0000
          Re: Importing variables non-deterministic? Chris Angelico <rosuav@gmail.com> - 2013-08-19 18:25 +0100
        Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 19:40 +0200
    Re: Importing variables non-deterministic? Chris Angelico <rosuav@gmail.com> - 2013-08-19 09:32 +0100
      Re: Importing variables non-deterministic? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-08-19 17:05 +0000
        Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 22:34 +0200
          Re: Importing variables non-deterministic? Steven D'Aprano <steve@pearwood.info> - 2013-08-20 05:48 +0000
            Re: Importing variables non-deterministic? wxjmfauth@gmail.com - 2013-08-19 23:40 -0700
            Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-20 08:55 +0200
              Re: Importing variables non-deterministic? wxjmfauth@gmail.com - 2013-08-20 00:31 -0700
                Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-20 09:55 +0200
                Re: Importing variables non-deterministic? wxjmfauth@gmail.com - 2013-08-20 02:15 -0700
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 11:03 +0200
    Re: Importing variables non-deterministic? Chris Angelico <rosuav@gmail.com> - 2013-08-19 10:18 +0100
    Re: Importing variables non-deterministic? Peter Otten <__peter__@web.de> - 2013-08-19 11:49 +0200
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 13:54 +0200
    Re: Importing variables non-deterministic? Dave Angel <davea@davea.name> - 2013-08-19 12:33 +0000
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 16:55 +0200
    Re: Importing variables non-deterministic? Chris Angelico <rosuav@gmail.com> - 2013-08-19 16:04 +0100
    Re: Importing variables non-deterministic? Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-08-19 19:25 +0200
    Re: Importing variables non-deterministic? Ben Finney <ben+python@benfinney.id.au> - 2013-08-20 11:14 +1000

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