h5file = tb.openFile('test.h5', mode='w', title='Test Array')
root = h5file.root
x = h5file.createCArray(root, 'x', tb.Float64Atom(), shape=(ndim, ndim))
x[:100, :100] = np.random.random(size=(100, 100))
h5file.close()
Building a huge numpy array using pytables