如何利用Python的PyQt库来管理线程

PyQt为在Python应用程序中构建图形用户界面提供了一个强大的框架。为了确保执行后台任务时 UI 更新流畅且响应灵敏，Qt 利用与主 GUI 线程同时运行的线程。然而，有效地使用线程需要仔细考虑。

正如 Maya Posch 的文章中所述，在使用 QThreads 时，重新实现 run 方法不应该是首选方法。相反，请考虑使用信号和槽来促进线程之间的通信。为了说明正确的实现，将提供一个实际示例。

PyQt 线程管理示例

在示例中，我们创建一个单独的工作线程来处理长计算而主 GUI 线程则管理图形界面。工作线程通过信号将状态更新传达给 GUI。

要开始计算，用户单击“开始”按钮。 “取消”按钮可用于终止操作并重置工作线程。请注意，通常不建议强制终止线程，但用于演示目的。

Python 代码

from PyQt4 import QtGui, QtCore
import sys
import random

class Example(QtCore.QObject):

    signalStatus = QtCore.pyqtSignal(str)

    def __init__(self, parent=None):
        super(self.__class__, self).__init__(parent)

        # Create a gui object.
        self.gui = Window()

        # Create a new worker thread.
        self.createWorkerThread()

        # Make any cross object connections.
        self._connectSignals()

        self.gui.show()


    def _connectSignals(self):
        self.gui.button_cancel.clicked.connect(self.forceWorkerReset)
        self.signalStatus.connect(self.gui.updateStatus)
        self.parent().aboutToQuit.connect(self.forceWorkerQuit)


    def createWorkerThread(self):

        # Setup the worker object and the worker_thread.
        self.worker = WorkerObject()
        self.worker_thread = QtCore.QThread()
        self.worker.moveToThread(self.worker_thread)
        self.worker_thread.start()

        # Connect any worker signals
        self.worker.signalStatus.connect(self.gui.updateStatus)
        self.gui.button_start.clicked.connect(self.worker.startWork)


    def forceWorkerReset(self):      
        if self.worker_thread.isRunning():
            print('Terminating thread.')
            self.worker_thread.terminate()

            print('Waiting for thread termination.')
            self.worker_thread.wait()

            self.signalStatus.emit('Idle.')

            print('building new working object.')
            self.createWorkerThread()


    def forceWorkerQuit(self):
        if self.worker_thread.isRunning():
            self.worker_thread.terminate()
            self.worker_thread.wait()


class WorkerObject(QtCore.QObject):

    signalStatus = QtCore.pyqtSignal(str)

    def __init__(self, parent=None):
        super(self.__class__, self).__init__(parent)

    @QtCore.pyqtSlot()        
    def startWork(self):
        for ii in range(7):
            number = random.randint(0,5000**ii)
            self.signalStatus.emit('Iteration: {}, Factoring: {}'.format(ii, number))
            factors = self.primeFactors(number)
            print('Number: ', number, 'Factors: ', factors)
        self.signalStatus.emit('Idle.')

    def primeFactors(self, n):
        i = 2
        factors = []
        while i * i  1:
            factors.append(n)
        return factors


class Window(QtGui.QWidget):

    def __init__(self):
        QtGui.QWidget.__init__(self)
        self.button_start = QtGui.QPushButton('Start', self)
        self.button_cancel = QtGui.QPushButton('Cancel', self)
        self.label_status = QtGui.QLabel('', self)

        layout = QtGui.QVBoxLayout(self)
        layout.addWidget(self.button_start)
        layout.addWidget(self.button_cancel)
        layout.addWidget(self.label_status)

        self.setFixedSize(400, 200)

    @QtCore.pyqtSlot(str)
    def updateStatus(self, status):
        self.label_status.setText(status)


if __name__=='__main__':
    app = QtGui.QApplication(sys.argv)
    example = Example(app)
    sys.exit(app.exec_())

此示例演示了 PyQt 应用程序中 QThreads 的正确使用，允许高效的后台操作而不冻结用户界面。