Events in Python

[Simon Pickles]

Hi,

I have a stackless python app, using twisted in parts (.internet and
..adbapi).

I need a little help getting pythonic after years of c++ hell.

I'd like to use a system of events and observers, like c++ boost.signal.

I'd like to be able to subscribe multiple callbacks to a single function
and cal them all using something like:

event.invoke("some data to send with invocation")

I'm thinking twisted callbacks do this:

def observe(self, f);
self.event.addcallback(f)

Are there other ways?

Thanks

Si

 

[Ivan Illarionov]

You may need Louie (http://louie.berlios.de)
Django (http://djangoproject.com) does the same in django.dispatch -
and Django version works about 33% faster.

Note that all those signals/events are very slow in Python.

--Ivan

 

[Bjoern Schliessmann]

Note that all those signals/events are very slow in Python.

Compared to what, did you measure something?

Regards,


Björn

 

[Ivan Illarionov]

Compared to what, did you measure something?

As example, instantiation of Model classes in Django (Model.__init__)
sends two signals (pre_init and post_init) - they are rarely used in
practice - but they make instantiation about two times slower. Yes, I
measured that.

The creator of Louie (Patrick K. O'Brien) himself seems to use them
only as an option that can be enabled/disabled in his projects (e.g.
Schevo) - because they are slow.

 

[alex23]

Hey Si,

The PEAK lib Trellis (http://peak.telecommunity.com/DevCenter/Trellis)
is worth checking out. I haven't had a chance to use it yet but am
keen to.

There are several other modules that may apply, I recommend searching
on the Python Package Index (http://pypi.python.org/pypi), for
"observer" or "dispatcher".

Hope this helps.

-alex23