Python GIL and multithreading

Question

I would like to separate my sigle-thread application to number of working threads. Just 1 question - what about performance of this action? If GIL prevents python from executing more than 1 thread at the time will I have any profit?

Another point (from c/c++ point of view) - as I know each thread, anyway, can be only executed exclusively, so in the lower level than python interpreter I have the same limitation.

Summary: Will the the python threads have lesser efficiency that 'native' thread in part of task switching?

Answer 1

Don't worry about the GIL. Depending on the kinds of things your program does (calculation vs. I/O) you will have different performance characteristics. If your program is I/O bound then you probably won't notice the GIL at all.

Another approach is to use the multiprocessing module where each process runs in its own OS process with its own Python runtime. You can take full advantage of multiple cores with this approach, and it's usually safer because you don't have to worry about synchronising access to shared memory.