[Python] can't use multiprocessing with class factory?

Send the (pickleable) factory and the arguments used to construct the instance,
not the unpickleable instance itself.

def g(factory, i):
cls = factory(i)
print cls._x

if __name__ == '__main__':
pool = mp.Pool(2)
pool.map(g, zip([class_factory] * 4, range(4)))

By the way, when asking for help like this, show us what your code did and
describe what results you want. It can often be hard to figure out exactly what
you mean by "work".

Only classes defined on the top level of a module are picklable (see
http://docs.python.org/dev/py3k/library/pickle#what-can-be-pickled-and-unpickled
). The collections.namedtuple class factory function works around this
limitation by setting the __module__ attribute of the created class,
but I'm not sure if this solution can be used in this case.


Daniel

namedtuple's trick only works when you assign the created class to a name at the
module level. E.g.

MyFancyTuple = collections.namedtuple(...)

The trick won't work for "anonymous" classes like the above use case.

What is the output?

2011/1/28, Alan <alan.isaac at gmail.com>:

If I change that to g((factory,i)) it does work.

Thanks!

Alan