Add has_wrapper_attr (Farama-Foundation#1070)

gymnasium/core.py

@@ -264,6 +264,10 @@ def __exit__(self, *args: Any):
         # propagate exception
         return False
 
+    def has_wrapper_attr(self, name: str) -> bool:
+        """Checks if the attribute `name` exists in the environment."""
+        return hasattr(self, name)
+
     def get_wrapper_attr(self, name: str) -> Any:
         """Gets the attribute `name` from the environment."""
         return getattr(self, name)
@@ -392,6 +396,13 @@ def wrapper_spec(cls, **kwargs: Any) -> WrapperSpec:
             kwargs=kwargs,
         )
 
+    def has_wrapper_attr(self, name: str) -> bool:
+        """Checks if the given attribute is within the wrapper or its environment."""
+        if hasattr(self, name):
+            return True
+        else:
+            return self.env.has_wrapper_attr(name)
+
     def get_wrapper_attr(self, name: str) -> Any:
         """Gets an attribute from the wrapper and lower environments if `name` doesn't exist in this object.
 

gymnasium/utils/play.py

@@ -70,15 +70,13 @@ def _get_relevant_keys(
         self, keys_to_action: dict[tuple[int], int] | None = None
     ) -> set:
         if keys_to_action is None:
-            if hasattr(self.env, "get_keys_to_action"):
-                keys_to_action = self.env.get_keys_to_action()
-            elif hasattr(self.env.unwrapped, "get_keys_to_action"):
-                keys_to_action = self.env.unwrapped.get_keys_to_action()
+            if self.env.has_wrapper_attr("get_keys_to_action"):
+                keys_to_action = self.env.get_wrapper_attr("get_keys_to_action")()
             else:
                 assert self.env.spec is not None
                 raise MissingKeysToAction(
                     f"{self.env.spec.id} does not have explicit key to action mapping, "
-                    "please specify one manually"
+                    "please specify one manually, `play(env, keys_to_action=...)`"
                 )
         assert isinstance(keys_to_action, dict)
         relevant_keys = set(sum((list(k) for k in keys_to_action.keys()), []))
@@ -244,10 +242,8 @@ def play(
     env.reset(seed=seed)
 
     if keys_to_action is None:
-        if hasattr(env, "get_keys_to_action"):
-            keys_to_action = env.get_keys_to_action()
-        elif hasattr(env.unwrapped, "get_keys_to_action"):
-            keys_to_action = env.unwrapped.get_keys_to_action()
+        if env.has_wrapper_attr("get_keys_to_action"):
+            keys_to_action = env.get_wrapper_attr("get_keys_to_action")()
         else:
             assert env.spec is not None
             raise MissingKeysToAction(

tests/test_core.py

@@ -168,22 +168,25 @@ def test_reward_observation_action_wrapper():
 
 def test_get_set_wrapper_attr():
     env = gym.make("CartPole-v1")
+    assert env is not env.unwrapped
 
     # Test get_wrapper_attr
     with pytest.raises(AttributeError):
         env.gravity
     assert env.unwrapped.gravity is not None
+    assert env.has_wrapper_attr("gravity")
     assert env.get_wrapper_attr("gravity") is not None
 
     with pytest.raises(AttributeError):
         env.unknown_attr
+    assert env.has_wrapper_attr("unknown_attr") is False
     with pytest.raises(AttributeError):
         env.get_wrapper_attr("unknown_attr")
 
     # Test set_wrapper_attr
     env.set_wrapper_attr("gravity", 10.0)
     with pytest.raises(AttributeError):
-        env.gravity
+        env.gravity  # checks the top level wrapper hasn't been updated
     assert env.unwrapped.gravity == 10.0
     assert env.get_wrapper_attr("gravity") == 10.0
 
@@ -195,10 +198,12 @@ def test_get_set_wrapper_attr():
     # Test with OrderEnforcing (intermediate wrapper)
     assert not isinstance(env, OrderEnforcing)
 
+    # show that the base and top level objects don't contain the attribute
     with pytest.raises(AttributeError):
         env._disable_render_order_enforcing
     with pytest.raises(AttributeError):
         env.unwrapped._disable_render_order_enforcing
+    assert env.has_wrapper_attr("_disable_render_order_enforcing")
     assert env.get_wrapper_attr("_disable_render_order_enforcing") is False
 
     env.set_wrapper_attr("_disable_render_order_enforcing", True)