Hi everyone, I started looking into improving the signal.lti class following the issue discussed at https://github.com/scipy/scipy/issues/2912 The pull request can be found here: https://github.com/scipy/scipy/pull/4576 The main idea is to split the lti class into ss, tf, and zpk subclasses. Calling the lti class itself returns instances of these three subclasses. Advantages * No redundant information (lti class currently holds the information of all 3 classes) * Reduce overhead (creating 3 system representations) * Switching between the different subclasses is more explicit: obj.ss(), obj.tf(), obj.zpk() * Avoids one huge class for everything * Is fully backwards compatible (as far as I can tell) * Similar to what Octave / Matlab does (easier to convert code from there to scipy) Disadvantages: * Accessing properties that are not part of the subclass is more expensive (e.g.: sys = ss(1,1,1,1); sys.num --> this now returns sys.tf().num). Any suggestions / comments / things I've broken? Best, Felix