Python api of placement group (#9243)

python/ray/experimental/__init__.py

@@ -1,8 +1,10 @@
 from .api import get, wait
 from .dynamic_resources import set_resource
-
+from .placement_group import (
+    placement_group, )
 __all__ = [
     "get",
     "wait",
     "set_resource",
+    "placement_group",
 ]

python/ray/experimental/placement_group.py

@@ -0,0 +1,26 @@
+import ray
+from typing import (List, Dict)
+
+
+def placement_group(bundles: List[Dict[str, float]],
+                    strategy: str = "PACK",
+                    name: str = None):
+    """
+    Create a placement group.
+
+    This method is the api to create placement group.
+
+    Args:
+        bundles: A list of bundles which represent the resources needed.
+        strategy: The strategy to create the placement group.
+            There are two build-in strategies for the time begin.
+            PACK: Packs Bundles close together inside processes or nodes as
+            tight as possible.
+            SPREAD: Places Bundles across distinct nodes or processes as even
+            as possible.
+        name: The name of the placement group.
+    """
+    worker = ray.worker.global_worker
+    placement_group_id = worker.core_worker.create_placement_group(
+        name, bundles, strategy)
+    return placement_group_id