Add Batch._reset_state for DRY. (#3169)

pubsub/google/cloud/pubsub/topic.py

@@ -444,20 +444,19 @@ class Batch(object):
     def __init__(self, topic, client, max_interval=_INFINITY,
                  max_messages=_INFINITY, max_size=1024 * 1024 * 9):
         self.topic = topic
+        self.client = client
         self.messages = []
         self.message_ids = []
-        self.client = client
 
         # Set the autocommit rules. If the interval or number of messages
         # is exceeded, then the .publish() method will imply a commit.
         self._max_interval = max_interval
         self._max_messages = max_messages
         self._max_size = max_size
 
-        # Set the initial starting timestamp (used against the interval)
-        # and initial size.
-        self._start_timestamp = time.time()
-        self._current_size = 0
+        # Set up the initial state, initializing messages, the starting
+        # timestamp, etc.
+        self._reset_state()
 
     def __enter__(self):
         return self
@@ -469,6 +468,13 @@ def __exit__(self, exc_type, exc_val, exc_tb):
     def __iter__(self):
         return iter(self.message_ids)
 
+    def _reset_state(self):
+        """Reset the state of this batch."""
+
+        del self.messages[:]
+        self._start_timestamp = time.time()
+        self._current_size = 0
+
     def publish(self, message, **attrs):
         """Emulate publishing a message, but save it.
 
@@ -526,6 +532,4 @@ def commit(self, client=None):
         api = client.publisher_api
         message_ids = api.topic_publish(self.topic.full_name, self.messages[:])
         self.message_ids.extend(message_ids)
-        del self.messages[:]
-        self._start_timestamp = time.time()
-        self._current_size = 0
+        self._reset_state()