deprecate ctrlutil.issys()

murrayrm · murrayrm · commit 1d670a7f702d · 2023-03-31T13:16:38.000-07:00
diff --git a/control/ctrlutil.py b/control/ctrlutil.py
@@ -44,6 +44,7 @@
 from . import lti
 import numpy as np
 import math
+import warnings
 
 __all__ = ['unwrap', 'issys', 'db2mag', 'mag2db']
 
@@ -99,6 +100,8 @@ def issys(obj):
     False
 
     """
+    warnings.warn("issys() is deprecated; use isinstance(obj, ct.LTI)",
+                  FutureWarning, stacklevel=2)
     return isinstance(obj, lti.LTI)
 
 def db2mag(db):
diff --git a/control/matlab/wrappers.py b/control/matlab/wrappers.py
@@ -5,7 +5,7 @@
 import numpy as np
 from ..iosys import ss
 from ..xferfcn import tf
-from ..ctrlutil import issys
+from ..lti import LTI
 from ..exception import ControlArgument
 from scipy.signal import zpk2tf
 from warnings import warn
@@ -124,7 +124,7 @@ def _parse_freqplot_args(*args):
     i = 0
     while i < len(args):
         # Check to see if this is a system of some sort
-        if issys(args[i]):
+        if isinstance(args[i], LTI):
             # Append the system to our list of systems
             syslist.append(args[i])
             i += 1
diff --git a/control/tests/ctrlutil_test.py b/control/tests/ctrlutil_test.py
@@ -1,7 +1,8 @@
 """ctrlutil_test.py"""
 
 import numpy as np
-
+import pytest
+import control as ct
 from control.ctrlutil import db2mag, mag2db, unwrap
 
 class TestUtils:
@@ -58,3 +59,8 @@ def test_mag2db(self):
     def test_mag2db_array(self):
         db_array = mag2db(self.mag)
         np.testing.assert_array_almost_equal(db_array, self.db)
+
+    def test_issys(self):
+        sys = ct.rss(2, 1, 1)
+        with pytest.warns(FutureWarning, match="deprecated; use isinstance"):
+            ct.issys(sys)
