Hi guys, I have a question regarding subclassing of the numpy.matrix class. I read through the wiki page, http://docs.scipy.org/doc/numpy/user/basics.subclassing.html and tried to subclass numpy.matrix, I find that if I override the __finalize_array__ method I have problems using the sum method and get the following error, Traceback (most recent call last): File "test.py", line 61, in <module> print (a * b).sum() File "/afs/ cern.ch/user/d/dvoong/programs/lib/python2.6/site-packages/numpy/matrixlib/defmatrix.py", line 435, in sum return N.ndarray.sum(self, axis, dtype, out)._align(axis) File "/afs/ cern.ch/user/d/dvoong/programs/lib/python2.6/site-packages/numpy/matrixlib/defmatrix.py", line 370, in _align return self[0,0] File "/afs/ cern.ch/user/d/dvoong/programs/lib/python2.6/site-packages/numpy/matrixlib/defmatrix.py", line 305, in __getitem__ out = N.ndarray.__getitem__(self, index) IndexError: 0-d arrays can only use a single () or a list of newaxes (and a single ...) as an index Can anyone help? It's my first time on this mailing list so apologies if this is not the right place to discuss this. Regards David Voong