[Python-Dev] Fwd: Deadlock by a second import in a thread

[Adam Olsen]

On 10/19/07, Facundo Batista <facundobatista at gmail.com> wrote:
> 2007/10/19, Adam Olsen <rhamph at gmail.com>:
>
> > The solution then is, if your python file will ever be imported, you
> > must write a main function and do all the work there instead.  Do not
> > write it in the style of a script (with significant work in the global
> > scope.)
>
> I had this a as a good coding style, not so mandatory.
>
> I agree with you that the OP shouldn't be doing that, but note that
> the main problem arises here because it's completely unpredictable the
> import in strptime for an external user.
>
> Do you recommend to close the bug as "won't fix" saying something like...
>
>     The deadlock happens because strptime has an import inside it, and
>     recursive imports are not allowed in different threads.
>
>     As a general rule and good coding style, don't run your code when the
>     module is imported, but put it in a function like "main" in the second file,
>     import it and call it from the first one. This will solve your problem.
>
>     Note that this happens to you with strptime, but could happen with a lot
>     of functions that do this internal import of something else. So,
> you'll never
>     be sure.
>
> What do you think?

Whether this is a minor problem due to poor style or a major problem
due to a language defect is a matter of perspective.  I'm working on
redesigning Python's threading support, expecting it to be used a
great deal more, which'd push it into the major problem category.

For now I'd leave it open.

-- 
Adam Olsen, aka Rhamphoryncus