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Re: I thought I understood how import worked...

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Roy Smith <roy@panix.com> writes:

> So, it appears that you *can* import a module twice, if you refer to
> it by different names! This is surprising.

The tutorial is misleading on this. It it says plainly:

    A module can contain executable statements as well as function
    definitions. […] They are executed only the *first* time the module
    is imported somewhere.

    <URL:http://docs.python.org/tutorial/modules.html>

but it doesn't make clear that a module can exist in the ‘sys.modules’
list multiple times under different names.

Care to file a documentation bug <URL:http://bugs.python.org/>
describing this?

> It means that having non-idempotent code which is executed at import
> time is a Bad Thing.

This is true whether or not the above about module imports is true. A
well-designed module should have top level code that performs idempotent
actions.

Be thankful that you've discovered this, and apply it well :-)

-- 
 \       “See, in my line of work you gotta keep repeating things over |
  `\       and over and over again, for the truth to sink in; to kinda |
_o__)               catapult the propaganda.” —George W. Bush, 2005-05 |
Ben Finney

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I thought I understood how import worked... Roy Smith <roy@panix.com> - 2012-08-07 09:18 -0400
  Re: I thought I understood how import worked... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 13:52 +0000
    Re: I thought I understood how import worked... Roy Smith <roy@panix.com> - 2012-08-07 08:25 -0700
      Re: I thought I understood how import worked... Paul Rubin <no.email@nospam.invalid> - 2012-08-07 08:53 -0700
      Re: I thought I understood how import worked... Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-07 17:54 +0000
    Re: I thought I understood how import worked... Cameron Simpson <cs@zip.com.au> - 2012-08-08 08:47 +1000
      Re: I thought I understood how import worked... Roy Smith <roy@panix.com> - 2012-08-07 19:05 -0400
      Re: I thought I understood how import worked... Ben Finney <ben+python@benfinney.id.au> - 2012-08-08 14:14 +1000
        Re: I thought I understood how import worked... Laszlo Nagy <gandalf@shopzeus.com> - 2012-08-08 08:40 +0200
        Re: I thought I understood how import worked... Roy Smith <roy@panix.com> - 2012-08-08 09:12 -0400
        Re: I thought I understood how import worked... Cameron Simpson <cs@zip.com.au> - 2012-08-09 15:52 +1000
  Re: I thought I understood how import worked... Ben Finney <ben+python@benfinney.id.au> - 2012-08-07 23:55 +1000
    Re: I thought I understood how import worked... Laszlo Nagy <gandalf@shopzeus.com> - 2012-08-07 16:14 +0200
    Re: I thought I understood how import worked... Roy Smith <roy@panix.com> - 2012-08-07 08:32 -0700
      Re: I thought I understood how import worked... Terry Reedy <tjreedy@udel.edu> - 2012-08-07 13:15 -0400
  Re: I thought I understood how import worked... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-07 15:10 +0100
  Re: I thought I understood how import worked... Terry Reedy <tjreedy@udel.edu> - 2012-08-07 12:49 -0400
  Re: I thought I understood how import worked... Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-07 18:44 +0100
  Re: I thought I understood how import worked... Jean-Michel Pichavant <jeanmichel@sequans.com> - 2012-08-08 10:47 +0200

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