gen_casadi_test: Fix instantiating np.array with list of MX objects

jackvreeken · jackvreeken · commit 649e22adb53a · 2021-02-15T20:14:15.000+01:00
Starting from, NumPy 1.20 behaves differently when instantiating arrays from array-like objects. NumPy used to be agnostic about the type of the object inside the list (MX in our case), but now it actually tries to interpret it as an array if it can. In this particular case, we deliberately _did not_ want this behavior. We use something akin to the work-around described in [0] to get the old behavior back. For more details, see: [0] https://numpy.org/devdocs/release/1.20.0-notes.html under "ArrayLike objects which do not define __len__ and __getitem__" or [1] numpy/numpy#17973
diff --git a/test/gen_casadi_test.py b/test/gen_casadi_test.py
@@ -724,7 +724,10 @@ def test_delay_for_loop_with_expand_vectors(self):
             ref_model = Model()
 
             def _array_mx(name, n):
-                return np.array([ca.MX.sym("{}[{}]".format(name, i+1)) for i in range(n)])
+                arr = np.empty(n, dtype=object)
+                for i in range(n):
+                    arr[i] = ca.MX.sym("{}[{}]".format(name, i+1))
+                return arr
 
             x = _array_mx("x", 3)
             y = _array_mx("y", 3)
