Opposite of yield?

[Mike C. Fletcher]

achrist at easystreet.com wrote:

>Peter Hansen wrote:
>  
>
>>Queue.Queue.get() ...
>>
>>    
>>
>
>That looks good.  But that needs a thread to block, right? 
>A generator manages to run without being a thread (at least
>overtly).  If we have the suck() statement, we also need 
>something that's the opposite of a generator (a Sucker?)
>and something that's the opposite of an iterator (a Suckee?). 
>I'm starting to get an idea why this is completely not all
>there. 
>  
>
You're probably looking for "watcher" or "dispatcher" patterns (using 
"pattern" loosely), i.e. something which is registered to respond to a 
particular type of "event" and process the results only when the event 
occurs.  See Patrick 's pydispatcher project for a fairly good framework 
on which to build such things.

http://pydispatcher.sourceforge.net/

In a more general sense, this is asynchronous programming, so at the 
high-end you could check out Twisted Matrix, which is a network-oriented 
asynchronous event system (pydispatcher is primarily an in-process system).

>The main question this raises is "How lightweight are threads?"
>Can I program with dozens or hundreds of python threads in a
>program (for example under Windows) and not notice that this is
>an inefficient or inept coding style?
>  
>
Large numbers of threads tend to cause problems eventually unless you're 
using micro-threads under Stackless Python.  Since AFAIK, micro-threads 
haven't been re-implemented in Stackless 3.0, massively-threading 
approaches aren't likely to be a great approach just yet.  As an aside, 
micro-threading, particularly when combined with continuations, allows 
for programming some of the most beautiful ways to deal with 
asynchronous events I've ever seen.

That said, a few dozen, or even hundred threads may run quite nicely 
under Windows.  Tim could likely give a better estimate, but I seem to 
recall him saying (way back when Stackless was 1.0) that Win95 could 
handle a far higher thread-load than Linux (possibly a few thousand 
threads?)  I really wouldn't try running a few thousand threads on most 
boxes, however, the OSes just aren't designed to handle it well.

HTH,
Mike

_______________________________________
  Mike C. Fletcher
  Designer, VR Plumber, Coder
  http://members.rogers.com/mcfletch/