[IPython-dev] pushing python class definition to engines

[Barry Wark]

If only we had a language in which code and data were interchangeable...
*LISP guru cries in the corner*

~Barry

On Tue, Jul 15, 2008 at 10:36 PM, Brian Granger <ellisonbg.net at gmail.com> wrote:
> Andrew,
>
> As Robert mentioned, this is really a limitation in how Python
> serializes classes and instances.  I have dealt with this in a couple
> of ways:
>
> 1.  Don't use classes :)  More, seriously though, functions, even
> those defined interactively can be pushed and pulled using
> push_function and pull_function.  There are only a few limitations,
> like no closures.
>
> 2.  Define your classes in a standalone module that can be imported by
> the engines, controller and client.  Then, you can push and pull
> instances just fine using push and pull.  This is mostly how I work -
> I develop classes in serial first, put them in a module and then
> simply import.
>
> Ironically, functions work better for this than classes.  Until Python
> has a different way of serializing classes and instances, we are
> stuck.
>
> Cheers,
>
> Brian
>
>
> On Tue, Jul 15, 2008 at 6:01 PM, Andrew Straw <strawman at astraw.com> 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?
>>
>> Traceback (most recent call last):
>>  File "flydra/test_ipython.py", line 14, in <module>
>>    mec.push_function(dict(MyObj= MyObj,))
>>  File
>> "/home/astraw/PY_ipython/lib/python2.5/site-packages/IPython/kernel/multiengineclient.py",
>> line 606, in push_function
>>    return self._blockFromThread(self.smultiengine.push_function,
>> namespace, targets=targets, block=block)
>>  File
>> "/home/astraw/PY_ipython/lib/python2.5/site-packages/IPython/kernel/multiengineclient.py",
>> line 456, in _blockFromThread
>>    result = blockingCallFromThread(function, *args, **kwargs)
>>  File
>> "/home/astraw/PY_ipython/lib/python2.5/site-packages/IPython/kernel/twistedutil.py",
>> line 69, in blockingCallFromThread
>>    return twisted.internet.threads.blockingCallFromThread(reactor, f,
>> *a, **kw)
>>  File
>> "/home/astraw/PY_ipython/lib/python2.5/site-packages/Twisted-8.1.0-py2.5-linux-x86_64.egg/twisted/internet/threads.py",
>> line 83, in blockingCallFromThread
>>    result.raiseException()
>>  File
>> "/home/astraw/PY_ipython/lib/python2.5/site-packages/Twisted-8.1.0-py2.5-linux-x86_64.egg/twisted/python/failure.py",
>> line 319, in raiseException
>>    raise self.type, self.value, self.tb
>> AttributeError: 'module' object has no attribute 'MyObj'
>>
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>>
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