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Date: Sat, 21 Jul 2012 12:26:35 -0400
From: Dave Angel <d@davea.name>
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To: Bruce Sherwood <bruce.sherwood@gmail.com>
Subject: Re: A thread import problem
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On 07/21/2012 10:54 AM, Bruce Sherwood wrote:
> Thanks much for this suggestion. I'm not sure I've correctly
> understood the operation "start_new_thread(lambda: __import__(<your
> module>), ())". By "your module" do you mean the user program which
> imported the module that will execute start_new_thread? It hadn't
> occurred to me to have A import B and B import A, though now that you
> describe this (if that's indeed what you mean) it makes sense. The
> original instance of A won't get past its initial import statement
> because the main loop won't return to it.
>
> Bruce Sherwood
>

Two of the things you mustn't do during an import:

1) start or end any threads
2) import something that's already in the chain of pending imports. 
(otherwise known as recursive imports, or import loop).  And there's a
special whammy reserved for those who import the script as though it
were a module.

Like any rule, there are possible exceptions.  But you're much better
off factoring your code better.

I haven't managed to understand your software description, so i'm not
making a specific suggestion.  But I know others have pointed out that
you should do as little as possible in top-level code of an imported
module.  Make the work happen in a function, and call that function from
the original script, not from inside some import.  An imported module's
top-level code should do nothing more complex than initialize module
constants.


-- 

DaveA