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Groups > comp.lang.python > #31046

Re: surprising behaviour of global dictionaries

Date 2012-10-09 12:10 -0400
From Dave Angel <d@davea.name>
Subject Re: surprising behaviour of global dictionaries
References <40ac555b-71c2-445e-814b-6bd1d037dbee@googlegroups.com> <mailman.2006.1349796256.27098.python-list@python.org> <b8a3d0c5-d6ba-42ef-a706-708b9148b594@googlegroups.com>
Newsgroups comp.lang.python
Message-ID <mailman.2009.1349799062.27098.python-list@python.org> (permalink)

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On 10/09/2012 11:36 AM, Michele Simionato wrote:
> On Tuesday, October 9, 2012 5:24:17 PM UTC+2, Peter Otten wrote:
>> Seriously, you shouldn't use the main script as a library; it is put into 
>>
>> the sys.modules cache under the "__main__" key. Subsequent imports under its 
>>
>> real name will not find that name in the cache and import another instance 
>>
>> of the module, with puzzling effects
> Actually I usually never use the main script as a library, this is why I never experience this puzzling behavior before. But now it is clear, thanks.
More generally, you should arrange your imports so that there are no
cycles.  If module/script "a" imports "b", directly or indirectly, "b"
should not try to import "a."  Move the common code to a third place,
and import it from both "a" and from "b".

The other symptoms you can get are more subtle than this one, but just
as surprising.


-- 

DaveA

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Thread

surprising behaviour of global dictionaries Michele Simionato <michele.simionato@gmail.com> - 2012-10-09 08:08 -0700
  Re: surprising behaviour of global dictionaries Peter Otten <__peter__@web.de> - 2012-10-09 17:24 +0200
    Re: surprising behaviour of global dictionaries Michele Simionato <michele.simionato@gmail.com> - 2012-10-09 08:36 -0700
      Re: surprising behaviour of global dictionaries Dave Angel <d@davea.name> - 2012-10-09 12:10 -0400
    Re: surprising behaviour of global dictionaries Michele Simionato <michele.simionato@gmail.com> - 2012-10-09 08:36 -0700
    Re: surprising behaviour of global dictionaries Grant Edwards <invalid@invalid.invalid> - 2012-10-09 15:53 +0000
      Re: surprising behaviour of global dictionaries Peter Otten <__peter__@web.de> - 2012-10-09 19:45 +0200

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