On Wed, May 6, 2009 at 4:08 PM, yoav glazner wrote:

Hi all, My Idea is to have a value returning Thread. I'll explain by example. <pycode> def foo():     time.sleep(20)     return 'bar' value = thread.startValueReturningThread(foo) #i need a better name for the function...) #here we do some work mg = moonGravity() mg.disable() #now we need the value that foo returned print value #this would be blocking untill foo is done! </pycode> This feature should provide a way to increase performance when possible with simple syntax. What do you think?

You're looking for the threadmethod decorator [1]. I'm not sure it's robust and useful enough to be included in the standard library though. George [1] http://code.activestate.com/recipes/440569/

MRAB writes:

I think it would be better if startValueReturningThread() returned what we could call a 'deferred result' object:

Or perhaps you just want to use Twisted. Regards Antoine.

On Wed, May 6, 2009 at 4:02 PM, Aahz wrote:

On Wed, May 06, 2009, yoav glazner wrote:

...

#now we need the value that foo returned print value #this would be blocking untill foo is done! </pycode>

This feature should provide a way to increase performance when possible with simple syntax.

Please provide more explanation for why the currently available features are insufficient.  Note that what you're asking for would change the semantics of Python at a very deep level and will almost certainly be rejected in its present form. -- Aahz (aahz@pythoncraft.com)           <*>         http://www.pythoncraft.com/

"It is easier to optimize correct code than to correct optimized code." --Bill Harlan _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

If the OP is asking for futures, couldn't that be implemented in a library without touching the language? It's a powerful enough feature to consider putting it in a library. It's going to be one of the 'primitives' of C++0x if one wanted a precedent (although I'm not suggesting everything C++ does is a good thing. Or even most of what C++ is a good thing).

On Thu, 2009-05-07 at 06:31 +0000, Antoine Pitrou wrote:

John Graham writes:

...

If the OP is asking for futures, couldn't that be implemented in a library without touching the language? It's a powerful enough feature to consider putting it in a library.

I don't know what C++ futures are but you should take a look at Twisted Deferred objects. The official implementation is in Python but a C implementation has been lingering on for years, you may be able to give them some help: http://twistedmatrix.com/trac/ticket/2245

Futures block, Defereds call forward. foo = something_returning_a_future() # does not block foo.get_value() # blocks def something_returning_a_future(): def worker(): [some code here that will does expensive work] return Future(worker) class Future: def __init__(callable): # imagine thread-safe code here to run callable in a thread def get_value(self): if not self.result: self.result = self.queue.pop() return self.result This is approximately a Future implementation for python. The difference - and its quite a big one - to Defereds is that defereds are a call-forward approach, whereas Futures are proxy objects that are waited on to get their results. twisted depends on never blocking as a core part of the design, Futures and Promises don't work well here. -Rob