From 3a3e4aed8624a68b89850051f0884b1ccb6336e8 Mon Sep 17 00:00:00 2001
From: Maltimore <git@maltimore.info>
Date: Tue, 12 Jan 2021 20:15:23 +0100
Subject: [PATCH] [RLlib] Add `__len__()` method to SampleBatch (#13371)

---
 rllib/policy/sample_batch.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/rllib/policy/sample_batch.py b/rllib/policy/sample_batch.py
index 08dfa2227..162c62499 100644
--- a/rllib/policy/sample_batch.py
+++ b/rllib/policy/sample_batch.py
@@ -86,6 +86,11 @@ class SampleBatch:
         # Keeps track of new columns added after initial ones.
         self.new_columns = []
 
+    @PublicAPI
+    def __len__(self):
+        """Returns the amount of samples in the sample batch."""
+        return self.count
+
     @staticmethod
     @PublicAPI
     def concat_samples(samples: List["SampleBatch"]) -> \