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.
源代码： Lib/asyncio/proactor_events.py , Lib/asyncio/windows_events.py , Lib/asyncio/windows_utils.py
3.8 版改变：
在 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.
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).
Pipes are not supported, so the
loop.connect_read_pipe()
and
loop.connect_write_pipe()
methods are not implemented.
子进程
are not supported, i.e.
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.
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.
macOS <= 10.8
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)