ADD: Add session ID property to the Live client

Author: nmacholl

CHANGELOG.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## 0.66.0 - TBD
+
+#### Enhancements
+- Added a property `Live.session_id` which returns the streaming session ID when the client is connected
+
 ## 0.65.0 - 2025-11-11
 
 #### Deprecations

databento/live/client.py

@@ -214,6 +214,19 @@ def port(self) -> int:
         """
         return self._port
 
+    @property
+    def session_id(self) -> str | None:
+        """
+        Return the session ID for the current session. If `None`, the client is
+        not connected.
+
+        Returns
+        -------
+        str | None
+
+        """
+        return self._session.session_id
+
     @property
     def symbology_map(self) -> dict[int, str | int]:
         """
@@ -365,7 +378,9 @@ def add_reconnect_callback(
 
         callback_name = getattr(reconnect_callback, "__name__", str(reconnect_callback))
         logger.info("adding user reconnect callback %s", callback_name)
-        self._session._user_reconnect_callbacks.append((reconnect_callback, exception_callback))
+        self._session._user_reconnect_callbacks.append(
+            (reconnect_callback, exception_callback),
+        )
 
     def start(
         self,

databento/live/session.py

@@ -72,7 +72,12 @@ def disable(self) -> None:
         """
         self._enabled.clear()
 
-    def put(self, item: DBNRecord, block: bool = True, timeout: float | None = None) -> None:
+    def put(
+        self,
+        item: DBNRecord,
+        block: bool = True,
+        timeout: float | None = None,
+    ) -> None:
         """
         Put an item on the queue if the queue is enabled.
 
@@ -498,6 +503,7 @@ def subscribe(
 
         with self._lock:
             if self._protocol is None:
+                self._session_id = None
                 self._connect(dataset=dataset)
 
             self._subscription_counter += 1
@@ -654,7 +660,10 @@ async def _reconnect(self) -> None:
 
                     should_restart = self.is_streaming()
                     if self._protocol._last_ts_event is not None:
-                        gap_start = pd.Timestamp(self._protocol._last_ts_event, tz="UTC")
+                        gap_start = pd.Timestamp(
+                            self._protocol._last_ts_event,
+                            tz="UTC",
+                        )
                     elif self._metadata.data is not None:
                         gap_start = pd.Timestamp(self._metadata.data.start, tz="UTC")
                     else:

tests/test_live_client.py

@@ -254,6 +254,7 @@ async def test_live_connect_auth(
     assert message.auth.endswith(live_client.key[-BUCKET_ID_LENGTH:])
     assert message.dataset == live_client.dataset
     assert message.encoding == Encoding.DBN
+    assert live_client.session_id is not None
 
 
 async def test_live_client_reuse(
@@ -273,8 +274,10 @@ async def test_live_client_reuse(
         message_type=gateway.AuthenticationRequest,
     )
 
+    first_session_id = live_client.session_id
     live_client.start()
     live_client.stop()
+    assert live_client.session_id == first_session_id
 
     await asyncio.sleep(1)
 
@@ -287,10 +290,14 @@ async def test_live_client_reuse(
         message_type=gateway.AuthenticationRequest,
     )
 
+    second_session_id = live_client.session_id
     live_client.start()
     live_client.stop()
     await live_client.wait_for_close()
 
+    assert live_client.session_id == second_session_id
+    assert first_session_id != second_session_id
+
 
 async def test_live_connect_auth_with_heartbeat_interval(
     mock_live_server: MockLiveServerInterface,