在 python3 中定义文件描述符 - 使用 pyudev/evdev

Posted 2023-03-30

【中文标题】在 python3 中定义文件描述符 - 使用 pyudev/evdev

【英文标题】：Defining a file descriptor in python3 - to work with pyudev/evdev

【发布时间】：2018-05-05 13:18:31

【问题描述】：

我目前正在尝试检测树莓派 3 上的蓝牙按钮的连接（该部分有效），一旦连接，检测按钮何时被按下（该部分无效）。

我从 evdev 提供的代码开始，并尝试对其进行调整以供我使用（见下文），但我无法创建正确的文件描述符以与 select 一起使用（如果我正确理解正在发生的事情）。

import functools
import pyudev
import evdev
from select import select

context = pyudev.Context()
monitor = pyudev.Monitor.from_netlink(context)
monitor.filter_by(subsystem='bluetooth')
monitor.start()

fds = monitor.fileno(): monitor
finalizers = []

while True:
    r, w, x = select(fds, [], [])

    if monitor.fileno() in r:
        r.remove(monitor.fileno())
        for udev in iter(functools.partial(monitor.poll, 0), None):
            devices = [evdev.InputDevice(fn) for fn in evdev.list_devices()]
            for device in devices:
                if device.name.strip() == 'AB Shutter3':
                    if udev.action == u'add':
                        print('Device added: %s' % udev)
                        fds[dev.fd] = device #This here breaks. dev.fd undefined.
                        break
                    if udev.action == u'remove':
                        print('Device removed: %s' % udev)
                        def helper():
                            global fds
                            fds = monitor.fileno(): monitor
                        finalizers.append(helper)
                        break

    for fd in r:
        dev = fds[fd]
        for event in dev.read():
            print(event)


    for i in range(len(finalizers)):
        finalizers.pop()()

问题是当我尝试添加设备时，没有定义 dev.fd。我试图定义它，但我不知道如何定义文件描述符。我该怎么办？

Device added: Device('/sys/devices/platform/soc/3f201000.serial/tty/ttyAMA0/hci0/hci0:64')
Traceback (most recent call last):
  File "dev_status.py", line 27, in <module>
    fds = dev.fd:device #This here breaks. dev.fd undefined.
NameError: name 'dev' is not defined

其他信息：运行 Raspbian Strech 和 Python 3.5.3 的 Raspberry Pi 3

另外，这是我关于 Stack Overflow 的第一个问题，所以如果有任何遗漏或可能更详细，请随时提及。

谢谢，

Pôm'

【参考方案1】：

好的，我已经设法找到了解决方案。在这里，如果它可以帮助任何人。

#!/usr/bin/env python3

import functools
import pyudev
import evdev
from select import select

context = pyudev.Context()
monitor = pyudev.Monitor.from_netlink(context)
monitor.filter_by(subsystem='bluetooth')
monitor.start()


fds = monitor.fileno(): monitor
time = 0.0

udevices = context.list_devices(subsystem='bluetooth')
link_up = False
for udevice in udevices :
    if udevice.device_type == 'link' and udevice.is_initialized :
        link_up = True
        print('yiha')

evdevices = [evdev.InputDevice(fn) for fn in evdev.list_devices()]

if len(evdevices) > 0:
    for evdevice in evdevices:
        if evdevice.name.strip() == 'AB Shutter3' and link_up:
            print('Device existing: %s' % udevice)
            fds[evdevice.fileno()] = evdevice

while True:
    r, w, x = select(fds, [], [])

    if monitor.fileno() in r:
        for udevice in iter(functools.partial(monitor.poll, 0), None):
            evdevices = [evdev.InputDevice(fn) for fn in evdev.list_devices()]
            for evdevice in evdevices:
                if evdevice.name.strip() == 'AB Shutter3':
                    if udevice.action == u'add':
                        print('Device added: %s' % udevice)
                        fds[evdevice.fileno()] = evdevice
                        break
                    if udevice.action == u'remove':
                        print('Device removed: %s' % udevice)
                        fds.pop(evdevice.fileno(),None) 
                        break

    if evdevice.fileno() in r:
        dev = fds[evdevice.fileno()]
        for event in dev.read():
            if event.type == evdev.ecodes.EV_KEY:
                data = evdev.categorize(event)
                if data.keystate == 1 and data.event.timestamp() - time > 0.05 :
                    if data.scancode == 115:
                        print("Big button")
                    elif data.scancode == 28:
                        print("Small button")
                time = data.event.timestamp()

我敢肯定，几个月后我会惊恐地看着这个，但就目前而言，它确实起到了作用。