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233b9da07d
Use "second", "millisecond", "microsecond", "nanosecond" instead of "sec", "ms", "msec", "us", "ns", etc.
105 lines
3 KiB
ReStructuredText
105 lines
3 KiB
ReStructuredText
.. currentmodule:: asyncio
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.. _asyncio-platform-support:
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================
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Platform Support
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================
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The :mod:`asyncio` module is designed to be portable,
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but some platforms have subtle differences and limitations
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due to the platforms' underlying architecture and capabilities.
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All Platforms
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=============
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* :meth:`loop.add_reader` and :meth:`loop.add_writer`
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cannot be used to monitor file I/O.
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Windows
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=======
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**Source code:** :source:`Lib/asyncio/proactor_events.py`,
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:source:`Lib/asyncio/windows_events.py`,
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:source:`Lib/asyncio/windows_utils.py`
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--------------------------------------
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.. versionchanged:: 3.8
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On Windows, :class:`ProactorEventLoop` is now the default event loop.
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All event loops on Windows do not support the following methods:
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* :meth:`loop.create_unix_connection` and
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:meth:`loop.create_unix_server` are not supported.
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The :data:`socket.AF_UNIX` socket family is specific to Unix.
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* :meth:`loop.add_signal_handler` and
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:meth:`loop.remove_signal_handler` are not supported.
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:class:`SelectorEventLoop` has the following limitations:
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* :class:`~selectors.SelectSelector` is used to wait on socket events:
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it supports sockets and is limited to 512 sockets.
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* :meth:`loop.add_reader` and :meth:`loop.add_writer` only accept
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socket handles (e.g. pipe file descriptors are not supported).
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* Pipes are not supported, so the :meth:`loop.connect_read_pipe`
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and :meth:`loop.connect_write_pipe` methods are not implemented.
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* :ref:`Subprocesses <asyncio-subprocess>` are not supported, i.e.
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:meth:`loop.subprocess_exec` and :meth:`loop.subprocess_shell`
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methods are not implemented.
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:class:`ProactorEventLoop` has the following limitations:
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* The :meth:`loop.add_reader` and :meth:`loop.add_writer`
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methods are not supported.
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The resolution of the monotonic clock on Windows is usually around 15.6
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milliseconds. The best resolution is 0.5 milliseconds. The resolution depends on the
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hardware (availability of `HPET
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<https://en.wikipedia.org/wiki/High_Precision_Event_Timer>`_) and on the
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Windows configuration.
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.. _asyncio-windows-subprocess:
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Subprocess Support on Windows
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-----------------------------
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On Windows, the default event loop :class:`ProactorEventLoop` supports
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subprocesses, whereas :class:`SelectorEventLoop` does not.
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The :meth:`policy.set_child_watcher()
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<AbstractEventLoopPolicy.set_child_watcher>` function is also
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not supported, as :class:`ProactorEventLoop` has a different mechanism
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to watch child processes.
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macOS
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=====
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Modern macOS versions are fully supported.
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.. rubric:: macOS <= 10.8
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On macOS 10.6, 10.7 and 10.8, the default event loop
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uses :class:`selectors.KqueueSelector`, which does not support
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character devices on these versions. The :class:`SelectorEventLoop`
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can be manually configured to use :class:`~selectors.SelectSelector`
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or :class:`~selectors.PollSelector` to support character devices on
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these older versions of macOS. Example::
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import asyncio
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import selectors
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selector = selectors.SelectSelector()
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loop = asyncio.SelectorEventLoop(selector)
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asyncio.set_event_loop(loop)
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