Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #59225

Re: PyMyth: Global variables are evil... WRONG!

Date 2013-11-12 11:45 -0600
From Tim Chase <python.list@tim.thechases.com>
Subject Re: PyMyth: Global variables are evil... WRONG!
References <7b97786a-2aaf-454c-8c3a-1c19d20d4345@googlegroups.com> <d1bb2f3b-d5d7-4336-8984-3871ecf5a16e@googlegroups.com> <d0b7995e-72c3-4c6d-bac3-d9f90bc91b39@googlegroups.com> <4bef88d0-d3eb-42e5-ac8e-288c629c528e@googlegroups.com> <2a325d8a-a242-4f2a-861b-9b786600f886@googlegroups.com>
Newsgroups comp.lang.python
Message-ID <mailman.2484.1384278220.18130.python-list@python.org> (permalink)

Show all headers | View raw

On 2013-11-12 09:00, Rick Johnson wrote:
> Because the constant PI should never change. Sure we can
> argue about granularity of PI, but that argument has no
> weight on the fact that PI should be a constant.
> 
> By placing PI in the module "math", we are creating a pseudo
> interface. We (the creators) are "assuming" that PI will be a
> constant and never change, and the caller is assuming that
> pi will remain static,  but not only can it be mutated, it
> can be mutated globally.

But the module-scoping of "globals" is perfectly valid:

 >>> print(math.PI)
 3.1415926535897932
 >>> print(Magnum.PI)
 "Tom Selleck"

As an example from the stdlib of setting globals via a protocol,
locale.setlocale() does exactly this.  So I'm not sure why you have
your knickers in a knot.  Module-level items can be accessed
globally (though often a bad idea, or at least you have to beware of
side-effects where other things might break), and if you don't like
the "modules are not objects", someone in this thread already showed
you that you can insert objects/classes into the sys.modules and get
full getter/setter functionality with minimal trouble.

Finally, we're all (mostly) consenting adults here.  If I want to be
an idiot and

  math.PI = 3.14

and suddenly stuff breaks, I get to keep all the pieces my breakage
caused.

-tkc

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-11 18:06 -0800
  Re: PyMyth: Global variables are evil... WRONG! Tim Daneliuk <tundra@tundraware.com> - 2013-11-11 20:47 -0600
    Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-11 20:46 -0800
      Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-12 16:02 +1100
      Re: PyMyth: Global variables are evil... WRONG! Ricardo Aráoz <ricaraoz@gmail.com> - 2013-11-12 07:15 -0300
      Re: PyMyth: Global variables are evil... WRONG! Tim Chase <python.list@tim.thechases.com> - 2013-11-12 05:32 -0600
      Re: PyMyth: Global variables are evil... WRONG! Terry Reedy <tjreedy@udel.edu> - 2013-11-12 20:20 -0500
      Re: PyMyth: Global variables are evil... WRONG! Tim Daneliuk <tundra@tundraware.com> - 2013-11-13 18:17 -0600
        Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 18:25 -0800
  Re: PyMyth: Global variables are evil... WRONG! jongiddy <jongiddy@gmail.com> - 2013-11-12 06:12 -0800
    Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-12 07:05 -0800
      Re: PyMyth: Global variables are evil... WRONG! jongiddy <jongiddy@gmail.com> - 2013-11-12 07:33 -0800
        Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-12 09:00 -0800
          Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-12 09:42 -0800
          Re: PyMyth: Global variables are evil... WRONG! Tim Chase <python.list@tim.thechases.com> - 2013-11-12 11:45 -0600
          Re: PyMyth: Global variables are evil... WRONG! jongiddy <jongiddy@gmail.com> - 2013-11-12 14:41 -0800
            Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-12 18:45 -0800
              Re: PyMyth: Global variables are evil... WRONG! Tim Chase <python.list@tim.thechases.com> - 2013-11-12 21:22 -0600
              Re: PyMyth: Global variables are evil... WRONG! Andrew Cooper <root@127.0.0.1> - 2013-11-13 22:00 +0000
                Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 18:16 -0800
  Re: PyMyth: Global variables are evil... WRONG! Alister <alister.ware@ntlworld.com> - 2013-11-12 14:32 +0000
    Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-13 02:22 +1100
  Re: PyMyth: Global variables are evil... WRONG! "Rhodri James" <rhodri@wildebst.demon.co.uk> - 2013-11-13 23:42 +0000
    Re: PyMyth: Global variables are evil... WRONG! Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-13 23:57 +0000
    Re: PyMyth: Global variables are evil... WRONG! Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-14 01:09 +0000
      Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 19:22 -0800
        Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-14 14:29 +1100
          Re: PyMyth: Global variables are evil... WRONG! Roy Smith <roy@panix.com> - 2013-11-13 23:33 -0500
            Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 20:40 -0800
            Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-14 15:53 +1100
            Re: PyMyth: Global variables are evil... WRONG! Steven D'Aprano <steve@pearwood.info> - 2013-11-14 06:25 +0000
          Re: PyMyth: Global variables are evil... WRONG! unknown <unknown@unknown.com> - 2013-11-14 09:41 +0000
    Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 18:10 -0800
      Re: PyMyth: Global variables are evil... WRONG! Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-14 02:45 +0000
        Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 19:45 -0800
          Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-13 20:01 -0800
          Re: PyMyth: Global variables are evil... WRONG! Steven D'Aprano <steve@pearwood.info> - 2013-11-14 05:50 +0000
            Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-14 09:26 -0800
              Re: PyMyth: Global variables are evil... WRONG! Joel Goldstick <joel.goldstick@gmail.com> - 2013-11-14 12:37 -0500
              Re: PyMyth: Global variables are evil... WRONG! Ethan Furman <ethan@stoneleaf.us> - 2013-11-14 09:56 -0800
                Re: PyMyth: Global variables are evil... WRONG! Alister <alister.ware@ntlworld.com> - 2013-11-14 20:12 +0000
                Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-15 09:43 +1100
              Re: PyMyth: Global variables are evil... WRONG! Joel Goldstick <joel.goldstick@gmail.com> - 2013-11-14 13:43 -0500
              Re: PyMyth: Global variables are evil... WRONG! Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-14 19:04 +0000
              Re: PyMyth: Global variables are evil... WRONG! Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-15 08:19 +0000
                Re: PyMyth: Global variables are evil... WRONG! Tim Daneliuk <tundra@tundraware.com> - 2013-11-15 09:26 -0600
                Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-16 02:42 +1100
                Re: PyMyth: Global variables are evil... WRONG! Tim Daneliuk <tundra@tundraware.com> - 2013-11-15 17:33 -0600
                Re: PyMyth: Global variables are evil... WRONG! Tim Daneliuk <tundra@tundraware.com> - 2013-11-15 17:33 -0600
                Re: PyMyth: Global variables are evil... WRONG! Rick Johnson <rantingrickjohnson@gmail.com> - 2013-11-15 20:01 -0800
                Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-16 15:19 +1100
                Re: PyMyth: Global variables are evil... WRONG! Chris Angelico <rosuav@gmail.com> - 2013-11-16 15:14 +1100

csiph-web