Hi all I am trying to create a subclass of the sparse matrix class in scipy, to add some extra methods I need. I have tried to follow the guide on: http://www.scipy.org/Subclasses but without much luck, the view method does not exist for the sparse matrix class. Below is a script I have created ----------------- #!/usr/bin/env python from scipy.sparse.csr import csr_matrix as spmatrix class sparsematrix_addons(spmatrix): """ subclass for standard scipy sparse class to add missing functionality """ def __new__(cls, matrix): obj = spmatrix.__init__(cls, matrix) return obj def square_spmat(self, M): return M ** 2 def ravel_spmat(self, M): pass if __name__ == '__main__': import numpy as np x = (np.random.rand(10, 10) * 2).astype(int).astype(float) xsp = sparsematrix_addons(x) -------------------- However, this generates the following error: TypeError: unbound method __init__() must be called with csr_matrix instance as first argument (got type instance instead) I am not strong in python OOP, or OOP in general, so I am sure this is a rather trivial problem to solve. Anyone got any solutions or ideas to point me in the right direction? Thanks in advance, Per