Set _remote() function args and kwargs as optional (#4305)

python/ray/actor.py

@@ -125,7 +125,11 @@ class ActorMethod(object):
     def remote(self, *args, **kwargs):
         return self._remote(args, kwargs)
 
-    def _remote(self, args, kwargs, num_return_vals=None):
+    def _remote(self, args=None, kwargs=None, num_return_vals=None):
+        if args is None:
+            args = []
+        if kwargs is None:
+            kwargs = {}
         if num_return_vals is None:
             num_return_vals = self._num_return_vals
 
@@ -233,8 +237,8 @@ class ActorClass(object):
         return self._remote(args=args, kwargs=kwargs)
 
     def _remote(self,
-                args,
-                kwargs,
+                args=None,
+                kwargs=None,
                 num_cpus=None,
                 num_gpus=None,
                 resources=None):
@@ -255,6 +259,11 @@ class ActorClass(object):
         Returns:
             A handle to the newly created actor.
         """
+        if args is None:
+            args = []
+        if kwargs is None:
+            kwargs = {}
+
         worker = ray.worker.get_global_worker()
         if worker.mode is None:
             raise Exception("Actors cannot be created before ray.init() "
@@ -293,10 +302,6 @@ class ActorClass(object):
                 actor_placement_resources = resources.copy()
                 actor_placement_resources["CPU"] += 1
 
-            if args is None:
-                args = []
-            if kwargs is None:
-                kwargs = {}
             function_name = "__init__"
             function_signature = self._method_signatures[function_name]
             creation_args = signature.extend_args(function_signature, args,