Drop support for Python 3.9.

aaugustin · aaugustin · commit 69ec85e67ace · 2025-07-14T15:03:39.000+02:00
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
@@ -55,7 +55,6 @@ jobs:
     strategy:
       matrix:
         python:
-          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
diff --git a/docs/intro/index.rst b/docs/intro/index.rst
@@ -6,7 +6,7 @@ Getting started
 Requirements
 ------------
 
-websockets requires Python ≥ 3.9.
+websockets requires Python ≥ 3.10.
 
 .. admonition:: Use the most recent Python release
     :class: tip
diff --git a/docs/project/changelog.rst b/docs/project/changelog.rst
@@ -25,13 +25,21 @@ fixing regressions shortly after a release.
 Only documented APIs are public. Undocumented, private APIs may change without
 notice.
 
-.. _15.1:
+.. _16.0:
 
-15.1
+16.0
 ----
 
 *In development*
 
+Backwards-incompatible changes
+..............................
+
+.. admonition:: websockets 16.0 requires Python ≥ 3.10.
+    :class: tip
+
+    websockets 15.0 is the last version supporting Python 3.9.
+
 Improvements
 ............
 
diff --git a/docs/topics/logging.rst b/docs/topics/logging.rst
@@ -133,8 +133,7 @@ Here's how to include them in logs, assuming they're in the
 
     async with serve(
         ...,
-        # Python < 3.10 requires passing None as the second argument.
-        logger=LoggerAdapter(logging.getLogger("websockets.server"), None),
+        logger=LoggerAdapter(logging.getLogger("websockets.server")),
     ):
         ...
 
@@ -176,8 +175,7 @@ a :class:`~logging.LoggerAdapter`::
 
     async with serve(
         ...,
-        # Python < 3.10 requires passing None as the second argument.
-        logger=LoggerAdapter(logging.getLogger("websockets.server"), None),
+        logger=LoggerAdapter(logging.getLogger("websockets.server")),
     ):
         ...
 
diff --git a/example/deployment/kubernetes/Dockerfile b/example/deployment/kubernetes/Dockerfile
@@ -1,4 +1,4 @@
-FROM python:3.9-alpine
+FROM python:3.13-alpine
 
 RUN pip install websockets
 
diff --git a/pyproject.toml b/pyproject.toml
@@ -5,7 +5,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "websockets"
 description = "An implementation of the WebSocket Protocol (RFC 6455 & 7692)"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = { text = "BSD-3-Clause" }
 authors = [
     { name = "Aymeric Augustin", email = "aymeric.augustin@m4x.org" },
@@ -19,7 +19,6 @@ classifiers = [
     "Operating System :: OS Independent",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
diff --git a/src/websockets/asyncio/client.py b/src/websockets/asyncio/client.py
@@ -579,7 +579,7 @@ async def __await_impl__(self) -> ClientConnection:
             # Re-raise exception with an informative error message.
             raise TimeoutError("timed out during opening handshake") from exc
 
-    # ... = yield from connect(...) - remove when dropping Python < 3.10
+    # ... = yield from connect(...) - remove when dropping Python < 3.11
 
     __iter__ = __await__
 
@@ -629,8 +629,7 @@ async def __aiter__(self) -> AsyncIterator[ClientConnection]:
                 self.logger.info(
                     "connect failed; reconnecting in %.1f seconds: %s",
                     delay,
-                    # Remove first argument when dropping Python 3.9.
-                    traceback.format_exception_only(type(exc), exc)[0].strip(),
+                    traceback.format_exception_only(exc)[0].strip(),
                 )
                 await asyncio.sleep(delay)
                 continue
diff --git a/src/websockets/asyncio/connection.py b/src/websockets/asyncio/connection.py
@@ -1224,11 +1224,7 @@ def broadcast(
             else:
                 connection.logger.warning(
                     "skipped broadcast: failed to write message: %s",
-                    traceback.format_exception_only(
-                        # Remove first argument when dropping Python 3.9.
-                        type(write_exception),
-                        write_exception,
-                    )[0].strip(),
+                    traceback.format_exception_only(write_exception)[0].strip(),
                 )
 
     if raise_exceptions and exceptions:
diff --git a/src/websockets/asyncio/server.py b/src/websockets/asyncio/server.py
@@ -834,7 +834,7 @@ async def __await_impl__(self) -> Server:
         self.server.wrap(server)
         return self.server
 
-    # ... = yield from serve(...) - remove when dropping Python < 3.10
+    # ... = yield from serve(...) - remove when dropping Python < 3.11
 
     __iter__ = __await__
 
diff --git a/src/websockets/datastructures.py b/src/websockets/datastructures.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from collections.abc import Iterable, Iterator, Mapping, MutableMapping
-from typing import Any, Protocol, Union
+from typing import Any, Protocol
 
 
 __all__ = [
@@ -171,13 +171,9 @@ def keys(self) -> Iterable[str]: ...
     def __getitem__(self, key: str) -> str: ...
 
 
-# Change to Headers | Mapping[str, str] | ... when dropping Python < 3.10.
-HeadersLike = Union[
-    Headers,
-    Mapping[str, str],
-    Iterable[tuple[str, str]],
-    SupportsKeysAndGetItem,
-]
+HeadersLike = (
+    Headers | Mapping[str, str] | Iterable[tuple[str, str]] | SupportsKeysAndGetItem
+)
 """
 Types accepted where :class:`Headers` is expected.
 
diff --git a/src/websockets/frames.py b/src/websockets/frames.py
@@ -7,7 +7,7 @@
 import secrets
 import struct
 from collections.abc import Generator, Sequence
-from typing import Callable, Union
+from typing import Callable
 
 from .exceptions import PayloadTooBig, ProtocolError
 
@@ -140,7 +140,7 @@ class Frame:
     """
 
     opcode: Opcode
-    data: Union[bytes, bytearray, memoryview]
+    data: bytes | bytearray | memoryview
     fin: bool = True
     rsv1: bool = False
     rsv2: bool = False
diff --git a/src/websockets/legacy/client.py b/src/websockets/legacy/client.py
@@ -607,16 +607,14 @@ async def __aiter__(self) -> AsyncIterator[WebSocketClientProtocol]:
                     self.logger.info(
                         "connect failed; reconnecting in %.1f seconds: %s",
                         initial_delay,
-                        # Remove first argument when dropping Python 3.9.
-                        traceback.format_exception_only(type(exc), exc)[0].strip(),
+                        traceback.format_exception_only(exc)[0].strip(),
                     )
                     await asyncio.sleep(initial_delay)
                 else:
                     self.logger.info(
                         "connect failed again; retrying in %d seconds: %s",
                         int(backoff_delay),
-                        # Remove first argument when dropping Python 3.9.
-                        traceback.format_exception_only(type(exc), exc)[0].strip(),
+                        traceback.format_exception_only(exc)[0].strip(),
                     )
                     await asyncio.sleep(int(backoff_delay))
                 # Increase delay with truncated exponential backoff.
@@ -673,7 +671,7 @@ async def __await_impl__(self) -> WebSocketClientProtocol:
             else:
                 raise SecurityError("too many redirects")
 
-    # ... = yield from connect(...) - remove when dropping Python < 3.10
+    # ... = yield from connect(...) - remove when dropping Python < 3.11
 
     __iter__ = __await__
 
diff --git a/src/websockets/legacy/protocol.py b/src/websockets/legacy/protocol.py
@@ -230,8 +230,6 @@ def __init__(
         self._paused = False
         self._drain_waiter: asyncio.Future[None] | None = None
 
-        self._drain_lock = asyncio.Lock()
-
         # This class implements the data transfer and closing handshake, which
         # are shared between the client-side and the server-side.
         # Subclasses implement the opening handshake and, on success, execute
@@ -1166,12 +1164,8 @@ def write_frame_sync(self, fin: bool, opcode: int, data: bytes) -> None:
 
     async def drain(self) -> None:
         try:
-            # drain() cannot be called concurrently by multiple coroutines.
-            # See https://github.com/python/cpython/issues/74116 for details.
-            # This workaround can be removed when dropping Python < 3.10.
-            async with self._drain_lock:
-                # Handle flow control automatically.
-                await self._drain()
+            # Handle flow control automatically.
+            await self._drain()
         except ConnectionError:
             # Terminate the connection if the socket died.
             self.fail_connection()
@@ -1626,11 +1620,7 @@ def broadcast(
             else:
                 websocket.logger.warning(
                     "skipped broadcast: failed to write message: %s",
-                    traceback.format_exception_only(
-                        # Remove first argument when dropping Python 3.9.
-                        type(write_exception),
-                        write_exception,
-                    )[0].strip(),
+                    traceback.format_exception_only(write_exception)[0].strip(),
                 )
 
     if raise_exceptions and exceptions:
diff --git a/src/websockets/legacy/server.py b/src/websockets/legacy/server.py
@@ -10,7 +10,7 @@
 import warnings
 from collections.abc import Awaitable, Generator, Iterable, Sequence
 from types import TracebackType
-from typing import Any, Callable, Union, cast
+from typing import Any, Callable, cast
 
 from ..asyncio.compatibility import asyncio_timeout
 from ..datastructures import Headers, HeadersLike, MultipleValuesError
@@ -48,8 +48,7 @@
 ]
 
 
-# Change to HeadersLike | ... when dropping Python < 3.10.
-HeadersLikeOrCallable = Union[HeadersLike, Callable[[str, Headers], HeadersLike]]
+HeadersLikeOrCallable = HeadersLike | Callable[[str, Headers], HeadersLike]
 
 HTTPResponse = tuple[StatusLike, HeadersLike, bytes]
 
@@ -706,7 +705,8 @@ def wrap(self, server: asyncio.base_events.Server) -> None:
             self.logger.info("server listening on %s", name)
 
         # Initialized here because we need a reference to the event loop.
-        # This should be moved back to __init__ when dropping Python < 3.10.
+        # This could be moved back to __init__ now that Python < 3.10 isn't
+        # supported anymore, but I'm not taking that risk in legacy code.
         self.closed_waiter = server.get_loop().create_future()
 
     def register(self, protocol: WebSocketServerProtocol) -> None:
@@ -1124,7 +1124,7 @@ async def __await_impl__(self) -> WebSocketServer:
         self.ws_server.wrap(server)
         return self.ws_server
 
-    # yield from serve(...) - remove when dropping Python < 3.10
+    # yield from serve(...) - remove when dropping Python < 3.11
 
     __iter__ = __await__
 
diff --git a/src/websockets/protocol.py b/src/websockets/protocol.py
@@ -4,7 +4,6 @@
 import logging
 import uuid
 from collections.abc import Generator
-from typing import Union
 
 from .exceptions import (
     ConnectionClosed,
@@ -39,8 +38,7 @@
     "SEND_EOF",
 ]
 
-# Change to Request | Response | Frame when dropping Python < 3.10.
-Event = Union[Request, Response, Frame]
+Event = Request | Response | Frame
 """Events that :meth:`~Protocol.events_received` may return."""
 
 
diff --git a/src/websockets/typing.py b/src/websockets/typing.py
@@ -2,7 +2,7 @@
 
 import http
 import logging
-from typing import TYPE_CHECKING, Any, NewType, Optional, Sequence, Union
+from typing import TYPE_CHECKING, Any, NewType, Sequence
 
 
 __all__ = [
@@ -18,8 +18,7 @@
 
 # Public types used in the signature of public APIs
 
-# Change to str | bytes when dropping Python < 3.10.
-Data = Union[str, bytes]
+Data = str | bytes
 """Types supported in a WebSocket message:
 :class:`str` for a Text_ frame, :class:`bytes` for a Binary_.
 
@@ -29,17 +28,15 @@
 """
 
 
-# Change to logging.Logger | ... when dropping Python < 3.10.
 if TYPE_CHECKING:
-    LoggerLike = Union[logging.Logger, logging.LoggerAdapter[Any]]
+    LoggerLike = logging.Logger | logging.LoggerAdapter[Any]
     """Types accepted where a :class:`~logging.Logger` is expected."""
 else:  # remove this branch when dropping support for Python < 3.11
-    LoggerLike = Union[logging.Logger, logging.LoggerAdapter]
+    LoggerLike = logging.Logger | logging.LoggerAdapter
     """Types accepted where a :class:`~logging.Logger` is expected."""
 
 
-# Change to http.HTTPStatus | int when dropping Python < 3.10.
-StatusLike = Union[http.HTTPStatus, int]
+StatusLike = http.HTTPStatus | int
 """
 Types accepted where an :class:`~http.HTTPStatus` is expected."""
 
@@ -55,8 +52,7 @@
 ExtensionName = NewType("ExtensionName", str)
 """Name of a WebSocket extension."""
 
-# Change to tuple[str, str | None] when dropping Python < 3.10.
-ExtensionParameter = tuple[str, Optional[str]]
+ExtensionParameter = tuple[str, str | None]
 """Parameter of a WebSocket extension."""
 
 
diff --git a/tests/asyncio/test_client.py b/tests/asyncio/test_client.py
diff --git a/tests/asyncio/test_connection.py b/tests/asyncio/test_connection.py
diff --git a/tests/asyncio/test_server.py b/tests/asyncio/test_server.py
diff --git a/tests/legacy/utils.py b/tests/legacy/utils.py
diff --git a/tests/sync/test_connection.py b/tests/sync/test_connection.py
diff --git a/tests/utils.py b/tests/utils.py
diff --git a/tox.ini b/tox.ini

-Original file line number
+Diff line change
     strategy:
       matrix:
         python:
 -          - "3.9"
           - "3.10"
           - "3.11"
           - "3.12"
Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-FROM python:3.9-alpine`
	`1`	`+FROM python:3.13-alpine`
`2`	`2`
`3`	`3`	`RUN pip install websockets`
`4`	`4`