| .. currentmodule:: asyncio |
| |
| |
| .. _asyncio-platform-support: |
| |
| |
| ================ |
| Platform Support |
| ================ |
| |
| The :mod:`asyncio` module is designed to be portable, |
| but some platforms have subtle differences and limitations |
| due to the platforms' underlying architecture and capabilities. |
| |
| |
| All Platforms |
| ============= |
| |
| * :meth:`loop.add_reader` and :meth:`loop.add_writer` |
| cannot be used to monitor file I/O. |
| |
| |
| Windows |
| ======= |
| |
| .. versionchanged:: 3.8 |
| |
| On Windows, :class:`ProactorEventLoop` is now the default event loop. |
| |
| All event loops on Windows do not support the following methods: |
| |
| * :meth:`loop.create_unix_connection` and |
| :meth:`loop.create_unix_server` are not supported. |
| The :data:`socket.AF_UNIX` socket family is specific to Unix. |
| |
| * :meth:`loop.add_signal_handler` and |
| :meth:`loop.remove_signal_handler` are not supported. |
| |
| :class:`SelectorEventLoop` has the following limitations: |
| |
| * :class:`~selectors.SelectSelector` is used to wait on socket events: |
| it supports sockets and is limited to 512 sockets. |
| |
| * :meth:`loop.add_reader` and :meth:`loop.add_writer` only accept |
| socket handles (e.g. pipe file descriptors are not supported). |
| |
| * Pipes are not supported, so the :meth:`loop.connect_read_pipe` |
| and :meth:`loop.connect_write_pipe` methods are not implemented. |
| |
| * :ref:`Subprocesses <asyncio-subprocess>` are not supported, i.e. |
| :meth:`loop.subprocess_exec` and :meth:`loop.subprocess_shell` |
| methods are not implemented. |
| |
| :class:`ProactorEventLoop` has the following limitations: |
| |
| * The :meth:`loop.add_reader` and :meth:`loop.add_writer` |
| methods are not supported. |
| |
| The resolution of the monotonic clock on Windows is usually around 15.6 |
| msec. The best resolution is 0.5 msec. The resolution depends on the |
| hardware (availability of `HPET |
| <https://en.wikipedia.org/wiki/High_Precision_Event_Timer>`_) and on the |
| Windows configuration. |
| |
| |
| .. _asyncio-windows-subprocess: |
| |
| Subprocess Support on Windows |
| ----------------------------- |
| |
| On Windows, the default event loop :class:`ProactorEventLoop` supports |
| subprocesses, whereas :class:`SelectorEventLoop` does not. |
| |
| The :meth:`policy.set_child_watcher() |
| <AbstractEventLoopPolicy.set_child_watcher>` function is also |
| not supported, as :class:`ProactorEventLoop` has a different mechanism |
| to watch child processes. |
| |
| |
| macOS |
| ===== |
| |
| Modern macOS versions are fully supported. |
| |
| .. rubric:: macOS <= 10.8 |
| |
| On macOS 10.6, 10.7 and 10.8, the default event loop |
| uses :class:`selectors.KqueueSelector`, which does not support |
| character devices on these versions. The :class:`SelectorEventLoop` |
| can be manually configured to use :class:`~selectors.SelectSelector` |
| or :class:`~selectors.PollSelector` to support character devices on |
| these older versions of macOS. Example:: |
| |
| import asyncio |
| import selectors |
| |
| selector = selectors.SelectSelector() |
| loop = asyncio.SelectorEventLoop(selector) |
| asyncio.set_event_loop(loop) |