You can use object as the dtype, which will allow arbitrary Python objects. I don't think there's any way of specializing a numpy array to accept only one particular class of Python object.

The path to hell is paved with premature optimization... As a beginner in python, focus on your program and what is supposed to do, once it is doing it too slowly you can ask focused questions about how to make it do it faster. I would stick with learning python's intrinsic data structures for managing your objects. You can implement your algorithms using using numpy arrays with standard data types if you are doing large array operations. Once you have some working code you can do performance testing to determine where you need optimization.

Numpy does allow you to create arrays of objects, and I will give you enough rope to hang yourself with below, but creating an ecosystem of tools to operate on those arrays of objects is not a trivial undertaking. You should first work with python data structures (buy Beazley's essential python reference), then with numpy's built in types, then creating your own compound numpy types. As a last resort, use the object type from the example below.

Good luck!

David

import numpy

class Atom(object):
    def atoms_method(self, foo, bar):
        #...with foo and bar being arrays of Paramsof length m & n
        atom_out = foo + bar
        return atom_out


array = numpy.ndarray((10,),dtype=numpy.object)

for i in xrange(10):
    array[i] = Atom()

for i in xrange(10):
    print array[i].atoms_method(i, 5)