• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1.. currentmodule:: asyncio
2
3
4.. _asyncio-platform-support:
5
6
7================
8Platform Support
9================
10
11The :mod:`asyncio` module is designed to be portable,
12but some platforms have subtle differences and limitations
13due to the platforms' underlying architecture and capabilities.
14
15
16All Platforms
17=============
18
19* :meth:`loop.add_reader` and :meth:`loop.add_writer`
20  cannot be used to monitor file I/O.
21
22
23Windows
24=======
25
26All event loops on Windows do not support the following methods:
27
28* :meth:`loop.create_unix_connection` and
29  :meth:`loop.create_unix_server` are not supported.
30  The :data:`socket.AF_UNIX` socket family is specific to Unix.
31
32* :meth:`loop.add_signal_handler` and
33  :meth:`loop.remove_signal_handler` are not supported.
34
35:class:`SelectorEventLoop` has the following limitations:
36
37* :class:`~selectors.SelectSelector` is used to wait on socket events:
38  it supports sockets and is limited to 512 sockets.
39
40* :meth:`loop.add_reader` and :meth:`loop.add_writer` only accept
41  socket handles (e.g. pipe file descriptors are not supported).
42
43* Pipes are not supported, so the :meth:`loop.connect_read_pipe`
44  and :meth:`loop.connect_write_pipe` methods are not implemented.
45
46* :ref:`Subprocesses <asyncio-subprocess>` are not supported, i.e.
47  :meth:`loop.subprocess_exec` and :meth:`loop.subprocess_shell`
48  methods are not implemented.
49
50:class:`ProactorEventLoop` has the following limitations:
51
52* The :meth:`loop.create_datagram_endpoint` method
53  is not supported.
54
55* The :meth:`loop.add_reader` and :meth:`loop.add_writer`
56  methods are not supported.
57
58The resolution of the monotonic clock on Windows is usually around 15.6
59msec.  The best resolution is 0.5 msec. The resolution depends on the
60hardware (availability of `HPET
61<https://en.wikipedia.org/wiki/High_Precision_Event_Timer>`_) and on the
62Windows configuration.
63
64
65.. _asyncio-windows-subprocess:
66
67Subprocess Support on Windows
68-----------------------------
69
70:class:`SelectorEventLoop` on Windows does not support subproceses.
71On Windows, :class:`ProactorEventLoop` should be used instead::
72
73  import asyncio
74
75  asyncio.set_event_loop_policy(
76      asyncio.WindowsProactorEventLoopPolicy())
77
78  asyncio.run(your_code())
79
80
81The :meth:`policy.set_child_watcher()
82<AbstractEventLoopPolicy.set_child_watcher>` function is also
83not supported, as :class:`ProactorEventLoop` has a different mechanism
84to watch child processes.
85
86
87macOS
88=====
89
90Modern macOS versions are fully supported.
91
92.. rubric:: macOS <= 10.8
93
94On macOS 10.6, 10.7 and 10.8, the default event loop
95uses :class:`selectors.KqueueSelector`, which does not support
96character devices on these versions.  The :class:`SelectorEventLoop`
97can be manually configured to use :class:`~selectors.SelectSelector`
98or :class:`~selectors.PollSelector` to support character devices on
99these older versions of macOS.  Example::
100
101    import asyncio
102    import selectors
103
104    selector = selectors.SelectSelector()
105    loop = asyncio.SelectorEventLoop(selector)
106    asyncio.set_event_loop(loop)
107