[IPython-dev] pushing python class definition to engines

[Robert Kern]

Andrew Straw wrote:
> After seeing Brian Granger's great demo of the parallel abilities in
> IPython last week at the SIAM conference, I'm playing with ipython trunk
> which I just pulled out of launchpad (for this reason, I'm posting on
> the -dev list).
> 
> Anyhow, if I start a client in the usual way:
> 
> from IPython.kernel import client
> mec = client.MultiEngineClient()
> 
> I can easily push Python integers:
> 
> a=5
> mec['a'] = a
> print mec.gather('a')
> 
> But pushing classes doesn't work:
> 
> class MyObj(object):
>     def __init__(self,x):
>         print 'PID',os.getpid()
>         self.x=x
> 
> mec['MyObj'] = MyObj
> print mec.gather('MyObj')
> 
> That gives the following error. How can I push a class definition to my
> engines?

It's really tricky since class objects normally don't really serialize. Pickles 
just contain a reference to the fully-qualified name of the class. In this case, 
it's __main__.MyObj. Since there is no MyObj in __main__ in your remote 
namespace, you get the error you see. You will have to push actual code to your 
remote kernels.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless enigma
  that is made terrible by our own mad attempt to interpret it as though it had
  an underlying truth."
   -- Umberto Eco