Allow string keys in `eval` utility (#242)

pytensor/graph/basic.py

@@ -597,6 +597,22 @@ class Variable(Node, Generic[_TypeType, OptionalApplyType]):
         if inputs_to_values is None:
             inputs_to_values = {}
 
+        def convert_string_keys_to_variables(input_to_values):
+            new_input_to_values = {}
+            for key, value in inputs_to_values.items():
+                if isinstance(key, str):
+                    matching_vars = get_var_by_name([self], key)
+                    if not matching_vars:
+                        raise Exception(f"{key} not found in graph")
+                    elif len(matching_vars) > 1:
+                        raise Exception(f"Found multiple variables with name {key}")
+                    new_input_to_values[matching_vars[0]] = value
+                else:
+                    new_input_to_values[key] = value
+            return new_input_to_values
+
+        inputs_to_values = convert_string_keys_to_variables(inputs_to_values)
+
         if not hasattr(self, "_fn_cache"):
             self._fn_cache = dict()
 

tests/graph/test_basic.py

@@ -302,6 +302,24 @@ class TestEval:
             pickle.loads(pickle.dumps(self.w)), "_fn_cache"
         ), "temporary functions must not be serialized"
 
+    def test_eval_with_strings(self):
+        assert self.w.eval({"x": 1.0, self.y: 2.0}) == 6.0
+        assert self.w.eval({self.z: 3}) == 6.0
+
+    def test_eval_with_strings_multiple_matches(self):
+        e = scalars("e")
+        t = e + 1
+        t.name = "e"
+        with pytest.raises(Exception, match="Found multiple variables with name e"):
+            t.eval({"e": 1})
+
+    def test_eval_with_strings_no_match(self):
+        e = scalars("e")
+        t = e + 1
+        t.name = "p"
+        with pytest.raises(Exception, match="o not found in graph"):
+            t.eval({"o": 1})
+
 
 class TestAutoName:
     def test_auto_name(self):