scipy/scipy — pull request #225 by bjornfor (2012-05-21 17:47:35+00:00)
Title: ENH: ltisys: make lti zpk initialization work with plain lists

lti objects can be created from a 3-tuple of zero-pole-gain (zpk)
values. However, the current code only accepts numpy.array arguments,
not plain lists.

This is OK:
>>> s = lti(array([]), array([-1]), 1)

This is not:
>>> s = lti([], [-1], 1)
[...]
AttributeError: 'list' object has no attribute 'shape'

Using plain Python lists is intuitive and user friendly, so make that
work as well.