A thread import problem

Dave Angel d at davea.name
Sat Jul 21 22:53:29 CEST 2012


On 07/21/2012 04:36 PM, Bruce Sherwood wrote:
> Thanks much for this clear statement. I hadn't managed to find any
> documentation on this specific issue.
>
> Bruce Sherwood
>
> On Sat, Jul 21, 2012 at 10:26 AM, Dave Angel <d at davea.name> wrote:
>> 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
>>
>>

(You top-posted, which makes it harder to figure out who said what.)

For docs on the threading thing, see:

http://docs.python.org/library/threading.html

" ... an import should not have the side effect of spawning a new thread
and then waiting for that thread in any way..."




-- 

DaveA




More information about the Python-list mailing list