在 Python 中作彤，檢測(cè)熱插拔事件（例如 USB 設(shè)備插入或移除）可以通過(guò)以下幾種方法實(shí)現(xiàn)覆山。最常用的方式是使用 pyudev 庫(kù)（適用于 Linux 系統(tǒng)）來(lái)監(jiān)聽系統(tǒng)設(shè)備的變化俐东。

1脖镀、問(wèn)題背景

用戶正在嘗試使用 Python 來(lái)檢測(cè)鼠標(biāo)和鍵盤事件公给，并在檢測(cè)過(guò)程中容忍熱插拔操作基协。用戶編寫的腳本可以自動(dòng)檢測(cè)運(yùn)行時(shí)環(huán)境中的鍵盤和鼠標(biāo)插件，并輸出所有鍵盤和鼠標(biāo)事件剑按。用戶使用了 evdev 和 pyudev 包來(lái)實(shí)現(xiàn)此功能疾就。腳本大部分都可以正常工作，包括鍵盤和鼠標(biāo)事件檢測(cè)以及插件檢測(cè)艺蝴。然而猬腰，每當(dāng)用戶拔出鼠標(biāo)時(shí)，都會(huì)發(fā)生許多奇怪的事情猜敢，導(dǎo)致腳本無(wú)法正常工作姑荷。

（1）每當(dāng)將鼠標(biāo)插入系統(tǒng)時(shí)，/dev/input/ 文件夾中都會(huì)生成兩個(gè)文件缩擂，包括 ./mouseX 和 ./eventX鼠冕。用戶嘗試通過(guò) cat 命令查看兩個(gè)源的輸出，發(fā)現(xiàn)確實(shí)有差異撇叁，但我不理解為什么 Linux 會(huì)在 ./eventX 已經(jīng)存在的情況下仍然會(huì)有 ./mouseX。

（2）每當(dāng)用戶拔下鼠標(biāo)時(shí)畦贸，./mouseX 拔下事件會(huì)首先發(fā)生陨闹，但我在 evdev 中沒(méi)有使用它，這會(huì)導(dǎo)致腳本失敗薄坏，因?yàn)?./eventX（腳本中讀取數(shù)據(jù)的位置）也會(huì)同時(shí)拔下趋厉，但我只能在下一輪中檢測(cè)到 ./eventX。我使用了一個(gè)技巧（腳本中的變量 i）來(lái)繞過(guò)這個(gè)問(wèn)題胶坠，但即使我能夠成功刪除鼠標(biāo)設(shè)備君账，select.select() 也會(huì)開始無(wú)限期地讀取輸入，即使我沒(méi)有對(duì)鍵盤輸入任何內(nèi)容沈善。

以下是腳本的內(nèi)容（根據(jù)先前帖子的答案進(jìn)行了修改）乡数，非常感謝您事先的關(guān)注椭蹄！

#!/usr/bin/env python

importpyudev

fromevdevimportInputDevice,list_devices,categorize

fromselectimportselect

context=pyudev.Context()

monitor=pyudev.Monitor.from_netlink(context)

monitor.filter_by(subsystem='input')

monitor.start()

devices=map(InputDevice,list_devices())

dev_paths=[]

finalizers=[]

fordevindevices:

if"keyboard"indev.name.lower():

dev_paths.append(dev.fn)

elif"mouse"indev.name.lower():

dev_paths.append(dev.fn)

devices=map(InputDevice,dev_paths)

devices={dev.fd:devfordevindevices}

devices[monitor.fileno()]=monitor

count=1

whileTrue:

r,w,x=select(devices, [], [])

ifmonitor.fileno()inr:

r.remove(monitor.fileno())

forudeviniter(functools.partial(monitor.poll,0),None):

# we're only interested in devices that have a device node

# (e.g. /dev/input/eventX)

ifnotudev.device_node:

break

# find the device we're interested in and add it to fds

fornamein(i['NAME']foriinudev.ancestorsif'NAME'ini):

# I used a virtual input device for this test - you

# should adapt this to your needs

if'mouse'inname.lower()and'event'inudev.device_node:

ifudev.action=='add':

print('Device added: %s'%udev)

dev=InputDevice(udev.device_node)

devices[dev.fd]=dev

break

ifudev.action=='remove':

print('Device removed: %s'%udev)

finalizers.append(udev.device_node)

break

forpathinfinalizers:

fordevindevices.keys():

ifdev!=monitor.fileno()anddevices[dev].fn==path:

print"delete the device from list"

deldevices[dev]

foriinr:

ifiindevices.keys()andcount!=0:

count=-1

foreventindevices[i].read():

count=count+1

print(categorize(event))

2、解決方案

答案1：

mouseX 和 eventX 之間的區(qū)別在于净赴，一般來(lái)說(shuō)绳矩，eventX 是 evdev 設(shè)備，而 mouseX 是“傳統(tǒng)”設(shè)備（例如玖翅，不支持各種 evdev ioctl）翼馆。

我不知道你發(fā)布的代碼出了什么問(wèn)題，但這里有一個(gè)代碼片段可以解決這個(gè)問(wèn)題金度。

#!/usr/bin/env python

importpyudev

importevdev

importselect

importsys

importfunctools

importerrno

context=pyudev.Context()

monitor=pyudev.Monitor.from_netlink(context)

monitor.filter_by(subsystem='input')

# NB: Start monitoring BEFORE we query evdev initially, so that if

# there is a plugin after we evdev.list_devices() we'll pick it up

monitor.start()

# Modify this predicate function for whatever you want to match against

defpred(d):

return"keyboard"ind.name.lower()or"mouse"ind.name.lower()

# Populate the "active devices" map, mapping from /dev/input/eventXX to

# InputDevice

devices={}

fordinmap(evdev.InputDevice,evdev.list_devices()):

ifpred(d):

printd

devices[d.fn]=d

# "Special" monitor device

devices['monitor']=monitor

whileTrue:

rs,_,_=select.select(devices.values(), [], [])

# Unconditionally ping monitor; if this is spurious this

# will no-op because we pass a zero timeout.? Note that

# it takes some time for udev events to get to us.

forudeviniter(functools.partial(monitor.poll,0),None):

ifnotudev.device_node:break

ifudev.action=='add':

ifudev.device_nodenotindevices:

print"Device added: %s"%udev

try:

devices[udev.device_node]=evdev.InputDevice(udev.device_node)

exceptIOError,e:

# udev reports MORE devices than are accessible from

# evdev; a simple way to check is see if the devinfo

# ioctl fails

ife.errno!=errno.ENOTTY:raise

pass

elifudev.action=='remove':

# NB: This code path isn't exercised very frequently,

# because select() will trigger a read immediately when file

# descriptor goes away, whereas the udev event takes some

# time to propagate to us.

ifudev.device_nodeindevices:

print"Device removed (udev): %s"%devices[udev.device_node]

deldevices[udev.device_node]

forrinrs:

# You can't read from a monitor

ifr.fileno()==monitor.fileno():continue

ifr.fnnotindevices:continue

# Select will immediately return an fd for read if it will

# ENODEV.? So be sure to handle that.

try:

foreventinr.read():

pass

printevdev.categorize(event)

exceptIOError,e:

ife.errno!=errno.ENODEV:raise

print"Device removed: %s"%r

deldevices[r.fn]

然后你可以用類似的方式來(lái)監(jiān)聽事件应媚。