问如何通过QSocketNotifier通知我管道已经准备好阅读了？
EN

Stack Overflow用户

提问于 2014-07-23 10:02:43

回答 2查看 1.2K关注 0票数 0

使用Python3.4，在Windows和Unix上，我的意思是使用QSocketNotifier来发现管道已经准备好读取。这是一种人为的例子，因为管道是在一个过程中使用的。无论如何，问题的症结是，当管道上有什么东西可读时，我必须采取行动。

我已经想出了下面的演示程序，但是QSocketNotifier从不发射它的已激活信号。我漏掉了什么明显的东西吗？

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import os


def can_read(fd):
   print('File {} can be read'.format(fd))


def start():
   print('Starting')
   reader, writer = os.pipe()
   notifier = QSocketNotifier(reader, QSocketNotifier.Read, w)
   notifier.setEnabled(True)
   notifier.activated.connect(can_read)
   os.write(writer, b'a')
   os.close(writer)


app = QApplication([])
QTimer.singleShot(0, start)
w = QMainWindow()
w.show()
app.exec_()

python

windows

unix

pyqt

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回答 2

Stack Overflow用户

回答已采纳

发布于 2014-07-23 10:58:07

实际上，这并不回答如何从可读管道接收通知，但它提供了跨平台的替代方案，即监视套接字(而不是管道)：

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
import socket

def _create_sock_pair(port=0):
    """Create socket pair.

    If socket.socketpair isn't available, we emulate it.
    """
    # See if socketpair() is available.
    have_socketpair = hasattr(socket, 'socketpair')
    if have_socketpair:
        client_sock, srv_sock = socket.socketpair()
        return client_sock, srv_sock

    # Create a non-blocking temporary server socket
    temp_srv_sock = socket.socket()
    temp_srv_sock.setblocking(False)
    temp_srv_sock.bind(('', port))
    port = temp_srv_sock.getsockname()[1]
    temp_srv_sock.listen(1)

    # Create non-blocking client socket
    client_sock = socket.socket()
    client_sock.setblocking(False)
    try:
        client_sock.connect(('localhost', port))
    except socket.error as err:
        # Error 10035 (operation would block) is not an error, as we're doing this with a
        # non-blocking socket.
        if err.errno != 10035:
            raise

    # Use select to wait for connect() to succeed.
    import select
    timeout = 1
    readable = select.select([temp_srv_sock], [], [], timeout)[0]
    if temp_srv_sock not in readable:
        raise Exception('Client socket not connected in {} second(s)'.format(timeout))
    srv_sock, _ = temp_srv_sock.accept()

    return client_sock, srv_sock


def can_read():
    print('Server can read')
    app.quit()


def write():
    print('Client writing')
    client_sock.send(b'a')
    client_sock.close()


app = QApplication([])

client_sock, srv_sock = _create_sock_pair()
notifier = QSocketNotifier(srv_sock.fileno(), QSocketNotifier.Read)
notifier.activated.connect(can_read)
write()

w = QMainWindow()
w.show()
app.exec_()
srv_sock.close()

票数 1

Stack Overflow用户

发布于 2014-07-23 10:43:59

可能与让变量超出范围有关。如果存储所有相关的片段(例如，包装在类中)，它就能工作。下面是我的解决方案(使用pyqt4，很抱歉)，它一直运行到窗口关闭为止：

from PyQt4.QtGui import *
from PyQt4.QtCore import *
import os

class win(QMainWindow):


    def can_read(self,fd):
       print('File {} can be read'.format(fd))


    def start(self):
       print('Starting')
       self.reader, self.writer = os.pipe()
       notifier = QSocketNotifier(self.reader, QSocketNotifier.Read, self)
       notifier.setEnabled(True)
       notifier.activated.connect(self.can_read)
       os.write(self.writer, b'a')
       os.close(self.writer)


app = QApplication([])
#QTimer.singleShot(0, start)
w = win()
w.start()
w.show()
app.exec_()