On Mar 16, 3:40 pm, "Gabriel Genellina" <[EMAIL PROTECTED]> wrote: > En Sat, 15 Mar 2008 11:57:44 -0200, Deepak Rokade <[EMAIL PROTECTED]> > 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
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