Moved stuff away from core. Made component interface more uniform.

homeassistant/util.py

@@ -38,3 +38,18 @@ def str_to_datetime(dt_str):
         return datetime.datetime.strptime(dt_str, DATE_STR_FORMAT)
     except ValueError:  # If dt_str did not match our format
         return None
+
+
+def split_entity_id(entity_id):
+    """ Splits a state entity_id into domain, object_id. """
+    return entity_id.split(".", 1)
+
+
+def filter_entity_ids(entity_ids, domain_filter=None, strip_domain=False):
+    """ Filter a list of entities based on domain. Setting strip_domain
+        will only return the object_ids. """
+    return [
+        split_entity_id(entity_id)[1] if strip_domain else entity_id
+        for entity_id in entity_ids if
+        not domain_filter or entity_id.startswith(domain_filter)
+        ]