Using threads in python is safe ?

[Deepak Rokade]

Thanks all for removing confusion about GIL,
one more question;
If jobs to be processed by threds is I/O bound would multithreading help
python to improve speed of application ?

Since I read that " multithreading is not a good strategy to improve speed
of python application."


On Mon, Mar 17, 2008 at 7:00 AM, Benjamin <musiccomposition at gmail.com>
wrote:

> On Mar 16, 3:40 pm, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
> wrote:
> > En Sat, 15 Mar 2008 11:57:44 -0200, Deepak Rokade <smartp... at gmail.com>
> > escribi�:
> >
> > > I want to use therads in my application. Going through the docs , I
> read
> > > about GIL.
> > > Now I am confused whether using threads in python is safe or not.
> >
> > > One thing I know that if I am accessing global variables in two or
> more
> > > threads I need to synchronize them
> > > using locking or such mechanism so that only one thread access them at
> a
> > > time.
> >
> > Yes, altough some operations are known to be atomic so you don't need a
> > lock in that cases. I think there is a list in the wiki somewhere
> http://wiki.python.org/moinor perhaps at the effbot's site
> http://www.effbot.org
> Even for atomic operations, you should lock, though. That is not
> consistent over different Python implementations and is not always
> going to be in same in CPython.
> >
> > > 1.  In order to support multi-threaded Python programs, there's a
> global
> > > lock that must be held
> > > by the current thread before it can safely access Python objects.
> > > Does this lock need to be held by python application script
> expliciltly
> > > before accessing any python object or
> > > interpreter takes acre of it ?
> >
> > No, the interpreter takes care of it. The GIL is a concern for those
> > writing extensions using the Python API.
> >
> > > 2. Does multithreaded python script need to held lock before calling
> any
> > > blocking I/O call?
> > > Or one should not worry about GIL while using python threads if job to
> be
> > > processed by thread does not call
> > > any global variables and thread unsafe Python/C extension ?
> >
> > Python code should not worry about the GIL. The problem would be, a
> > callback written in Python for a not-thread-aware extension that had
> > released the GIL.
> >
> > --
> > Gabriel Genellina
>
> --
> http://mail.python.org/mailman/listinfo/python-list
>



-- 
Thanx & Regards,
Deepak Rokade

Do what u Enjoy &
Enjoy what u Do...........
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