The asyncio
module is designed to be portable, but some platforms have subtle differences and limitations due to the platforms’ underlying architecture and capabilities.
loop.add_reader()
and loop.add_writer()
cannot be used to monitor file I/O.Source code: Lib/asyncio/proactor_events.py, Lib/asyncio/windows_events.py, Lib/asyncio/windows_utils.py
Changed in version 3.8: On Windows, ProactorEventLoop
is now the default event loop.
All event loops on Windows do not support the following methods:
loop.create_unix_connection()
and loop.create_unix_server()
are not supported. The socket.AF_UNIX
socket family is specific to Unix.loop.add_signal_handler()
and loop.remove_signal_handler()
are not supported.SelectorEventLoop
has the following limitations:
SelectSelector
is used to wait on socket events: it supports sockets and is limited to 512 sockets.loop.add_reader()
and loop.add_writer()
only accept socket handles (e.g. pipe file descriptors are not supported).loop.connect_read_pipe()
and loop.connect_write_pipe()
methods are not implemented.loop.subprocess_exec()
and loop.subprocess_shell()
methods are not implemented.ProactorEventLoop
has the following limitations:
loop.add_reader()
and 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) and on the Windows configuration.
On Windows, the default event loop ProactorEventLoop
supports subprocesses, whereas SelectorEventLoop
does not.
The policy.set_child_watcher()
function is also not supported, as ProactorEventLoop
has a different mechanism to watch child processes.
Modern macOS versions are fully supported.
On macOS 10.6, 10.7 and 10.8, the default event loop uses selectors.KqueueSelector
, which does not support character devices on these versions. The SelectorEventLoop
can be manually configured to use SelectSelector
or 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)
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Licensed under the PSF License.
https://docs.python.org/3.9/library/asyncio-platforms.html