[Python-Dev] Twisted Isn't Specific (was Re: Trial balloon: microthreads library in stdlib) (original) (raw)

Bob Ippolito bob at redivi.com
Thu Feb 15 11:11:09 CET 2007

On 2/14/07, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Thomas Wouters wrote:

> I don't like the idea of something in the Python installation > deciding which reactor to use. I wouldn't mind if some way were provided of changing the reactor if you want. I'd just like to see a long term goal of making it unnecessary as far as possible. > In any case, your idea requires a lot of changes in external, non-Python > code -- PyGTK simply exposes the GTK mainloop, which couldn't care less > about Python's idea of a perfect event reactor model. On unix at least, I don't think it should be necessary to change gtk, only pygtk. If it can find out the file descriptor of the connection to the X server, it can plug that into the reactor, and then call gtkmainiterationdo() whenever something comes in on it. A similar strategy ought to work for any X11-based toolkit that exposes a function to perform one iteration of its main loop. Mileage on other platforms may vary. > The PerfectReactor can be added later, all current reactors > aliased to it, and no one would have to change a single line > of code. Sure. The other side to all this is the client side, i.e. the code that installs event callbacks. At the moment there's no clear direction to take, so everyone makes their own choice -- some use asyncore, some use Twisted, some use the gtk event loop, some roll their own, etc.

There is no single PerfectReactor. There are several use cases where you need to wait on >1 different event systems, which guarantees at least two OS threads (and two event loops). In general it's nice to have a single Python event loop ("the reactor") to act on said threads (e.g. something just sitting on a mutex waiting for messages) but waiting for IO to occur should probably happen on one or more ancillary threads -- one per event system (e.g. select, GTK, WaitForMultipleEvents, etc.)

-bob

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