[英]File to socket adapter in python
I want to use the asyncio library on Windows to read file-like objects (such as sys.stdin
and serial ports ). 我想在Windows上使用asyncio库来读取类似文件的对象(例如
sys.stdin
和serial ports )。
However, asyncio
on Windows expects readable objects to be sockets . 但是,Windows上的
asyncio
期望可读对象为sockets 。
Is it possible to write an adapter class to wrap a file-like object with the API of a socket so that I could use stdin
and serial ports with asyncio
? 是否可以编写一个适配器类来使用套接字的API包装类似文件的对象,以便我可以将
stdin
和串行端口与asyncio
一起asyncio
?
If so, please could you give an example because I've never used sockets before? 如果是这样,请给我一个例子,因为我以前从未使用过套接字吗?
No and maybe yes. 不,也许是。
You can't just wrap a file-like object as a socket, or vice-versa, and expect it to work. 您不能只是将类似文件的对象包装为套接字,反之亦然,并且期望它能工作。
asyncio
is using system calls under the hood to do its async magic and stdin
is stdin
from the system's point of view no mater how much you wrap it. asyncio
使用系统调用来执行其异步魔术,从系统的角度来看, stdin
是stdin
,无论包装多少。 When using the default SelectorEventLoop
it uses one of the select -like system calls. 使用默认的
SelectorEventLoop
它会使用类似select的系统调用之一。 On Windows it uses the select
system call, which does not support anything but sockets. 在Windows上它使用
select
系统调用,它不支持什么,但插座。
So, select
sucks on windows. 因此,
select
在窗口上烂透了。 Is there another option? 还有其他选择吗? Yes.
是。 On Windows, and only Windows, there is another API for doing async operations called
IOCP (I/O Completion Ports)
. 在Windows(仅Windows)上,还有另一个API用于执行异步操作,称为
IOCP (I/O Completion Ports)
。 It's a "notify-on-completion"
type multiplexer as opposed to the select
based "notify-when-ready"
type multiplexers. 它是
"notify-on-completion"
类型的多路复用器,而不是基于select
的"notify-when-ready"
类型的多路复用器。 The API is much more complicated than doing a simple select
call on a file, but fortunately asyncio
has some support for it already. 该API比对文件进行简单的
select
调用要复杂得多,但是幸运的是asyncio
已经对此文件提供了一些支持。
The ProactorEventLoop
uses IOCP on Windows and it should theoretically supports reading from stdin
. ProactorEventLoop
在Windows上使用IOCP,并且理论上应该支持从stdin
读取。 I don't have access to a Windows machine so I can't test this, but give this a go: 我无权使用Windows计算机,因此无法测试,但请尝试一下:
# vim: filetype=python3 tabstop=2 expandtab
import asyncio as aio
import os
import sys
if os.name == "nt":
proactor_loop = aio.ProactorEventLoop()
aio.set_event_loop(proactor_loop)
@aio.coroutine
def main(loop):
stdin_reader = aio.StreamReader()
stdin_transport, stdin_protocol = yield from loop.connect_read_pipe(
lambda: aio.StreamReaderProtocol(stdin_reader),
sys.stdin
)
line = yield from stdin_reader.read()
print(line.strip().decode("utf-8"))
stdin_transport.close()
loop = aio.get_event_loop()
loop.run_until_complete(main(loop))
loop.close()
And run the equivalent of this on Windows: 并在Windows上运行等效的命令:
$ echo blha blha blha | python test.py
blha blha blha
If this works, then at least you can do async stdin
on Windows. 如果可行,那么至少您可以在Windows上执行异步
stdin
。 And then you could try something similar for stdout/stderr
or perhaps even serial ports. 然后您可以为
stdout/stderr
甚至串行端口尝试类似的操作。
If all else fails, you could always simulate async behaviour by wrapping blocking calls in threads using the loop.run_in_executor
coroutine: 如果所有其他方法均失败,则始终可以通过使用
loop.run_in_executor
协程将阻塞调用包装在线程中来模拟异步行为:
yield from loop.run_in_executor(None, sys.stdin.readline)
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