It seems that if you enter the if statement here then it replaces self.A withself.A with zeros(1,1) which is of type ndarray. This will cause problems later as the library is taking advantage of the fact that * is matrix multiplication not elementwise multiplcation as it would be for ndarrays.

Here is an example of the problem

sys1 = control.StateSpace(0,0,0,0)
sys2 = control.StateSpace(1,0,0,0)
print "type(sys1.A)", type(sys1.A)
print "type(sys2.A)", type(sys2.A)


type(sys1.A) <type 'numpy.ndarray'>
type(sys2.A) <class 'numpy.matrixlib.defmatrix.matrix'>