use isdtime in StateSpace.__str__()

bnavigator · bnavigator · commit 89c22c160a6d · 2021-04-11T18:51:29.000+02:00
diff --git a/control/statesp.py b/control/statesp.py
@@ -391,11 +391,11 @@ def __str__(self):
                                "\n    ".join(str(M).splitlines()))
             for Mvar, M in zip(["A", "B", "C", "D"],
                                [self.A, self.B, self.C, self.D])])
-        # TODO: replace with standard calls to lti functions
-        if (type(self.dt) == bool and self.dt is True):
-            string += "\ndt unspecified\n"
-        elif (not (self.dt is None) and type(self.dt) != bool and self.dt > 0):
-            string += "\ndt = " + self.dt.__str__() + "\n"
+        if self.isdtime(strict=True):
+            if self.dt is True:
+                string += "\ndt unspecified\n"
+            else:
+                string += f"\ndt = {self.dt}\n"
         return string
 
     # represent to implement a re-loadable version
diff --git a/control/tests/statesp_test.py b/control/tests/statesp_test.py
@@ -745,7 +745,7 @@ def test_str(self, sys322):
         tsysdtunspec = StateSpace(tsys.A, tsys.B, tsys.C, tsys.D, True)
         assert str(tsysdtunspec) == tref + "\ndt unspecified\n"
         sysdt1 = StateSpace(tsys.A, tsys.B, tsys.C, tsys.D, 1.)
-        assert str(sysdt1) == tref + "\ndt = 1.0\n"
+        assert str(sysdt1) == tref + "\ndt = {}\n".format(1.)
 
     def test_pole_static(self):
         """Regression: pole() of static gain is empty array."""
