Question

我读了这篇文章How To Really, Truly Use QThreads; The Full Explanation，它说的不是子类qthread，而是重新实现run（），应该使用moveToThread使用moveToThread（QThread *）将QObject推送到QThread实例

这是c ++示例，但我不知道如何将其转换为python代码。

class Worker : public QObject
 {
     Q_OBJECT
     QThread workerThread;

 public slots:
     void doWork(const QString &parameter) {
         // ...
         emit resultReady(result);
     }

 signals:
     void resultReady(const QString &result);
 };

 class Controller : public QObject
 {
     Q_OBJECT
     QThread workerThread;
 public:
     Controller() {
         Worker *worker = new Worker;
         worker->moveToThread(&workerThread);
         connect(workerThread, SIGNAL(finished()), worker, SLOT(deleteLater()));
         connect(this, SIGNAL(operate(QString)), worker, SLOT(doWork(QString)));
         connect(worker, SIGNAL(resultReady(QString)), this, SLOT(handleResults(QString)));
         workerThread.start();
     }
     ~Controller() {
         workerThread.quit();
         workerThread.wait();
     }
 public slots:
     void handleResults(const QString &);
 signals:
     void operate(const QString &);
 };



QThread* thread = new QThread;
Worker* worker = new Worker();
worker->moveToThread(thread);
connect(worker, SIGNAL(error(QString)), this, SLOT(errorString(QString)));
connect(thread, SIGNAL(started()), worker, SLOT(process()));
connect(worker, SIGNAL(finished()), thread, SLOT(quit()));
connect(worker, SIGNAL(finished()), worker, SLOT(deleteLater()));
connect(thread, SIGNAL(finished()), thread, SLOT(deleteLater()));
thread->start();

我一直在使用这种方法来生成qthread，但正如您所看到的，它使用了不推荐的方式。如何重新编写它以使用首选方法？

class GenericThread(QThread):
    def __init__(self, function, *args, **kwargs):
        QThread.__init__(self)
        # super(GenericThread, self).__init__()

        self.function = function
        self.args = args
        self.kwargs = kwargs

    def __del__(self):
        self.wait()

    def run(self, *args):
        self.function(*self.args, **self.kwargs)

编辑：两年后...... 我尝试了qris的代码，它可以在不同的线程中运行

import sys
import time
from PyQt4 import QtCore, QtGui
from PyQt4.QtCore import pyqtSignal, pyqtSlot
import threading


def logthread(caller):
    print('%-25s: %s, %s,' % (caller, threading.current_thread().name,
                              threading.current_thread().ident))


class MyApp(QtGui.QWidget):

    def __init__(self, parent=None):
        QtGui.QWidget.__init__(self, parent)

        self.setGeometry(300, 300, 280, 600)
        self.setWindowTitle('using threads')

        self.layout = QtGui.QVBoxLayout(self)

        self.testButton = QtGui.QPushButton("QThread")
        self.testButton.released.connect(self.test)
        self.listwidget = QtGui.QListWidget(self)

        self.layout.addWidget(self.testButton)
        self.layout.addWidget(self.listwidget)

        self.threadPool = []
        logthread('mainwin.__init__')

    def add(self, text):
        """ Add item to list widget """
        logthread('mainwin.add')
        self.listwidget.addItem(text)
        self.listwidget.sortItems()

    def addBatch(self, text="test", iters=6, delay=0.3):
        """ Add several items to list widget """
        logthread('mainwin.addBatch')
        for i in range(iters):
            time.sleep(delay)  # artificial time delay
            self.add(text+" "+str(i))

    def test(self):
        my_thread = QtCore.QThread()
        my_thread.start()

        # This causes my_worker.run() to eventually execute in my_thread:
        my_worker = GenericWorker(self.addBatch)
        my_worker.moveToThread(my_thread)
        my_worker.start.emit("hello")
        # my_worker.finished.connect(self.xxx)

        self.threadPool.append(my_thread)
        self.my_worker = my_worker


class GenericWorker(QtCore.QObject):

    start = pyqtSignal(str)
    finished = pyqtSignal()

    def __init__(self, function, *args, **kwargs):
        super(GenericWorker, self).__init__()
        logthread('GenericWorker.__init__')
        self.function = function
        self.args = args
        self.kwargs = kwargs
        self.start.connect(self.run)

    @pyqtSlot()
    def run(self, *args, **kwargs):
        logthread('GenericWorker.run')
        self.function(*self.args, **self.kwargs)
        self.finished.emit()


# run
app = QtGui.QApplication(sys.argv)
test = MyApp()
test.show()
app.exec_()

输出是：

mainwin.__init__         : MainThread, 140221684574016,
GenericWorker.__init__   : MainThread, 140221684574016,
GenericWorker.run        : Dummy-1, 140221265458944,
mainwin.addBatch         : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,
mainwin.add              : Dummy-1, 140221265458944,

Answer 1

QThread中的默认run（）实现为您运行一个事件循环，相当于：

class GenericThread(QThread):
    def run(self, *args):
        self.exec_()

关于事件循环的重要一点是，它允许线程拥有的对象在其插槽上接收事件，这些事件将在该线程中执行。那些对象只是QObjects，而不是QThreads。

重要提示：QThread对象不属于自己的线程！它是在主线程上创建的并且存在于那里。除了run方法之外，它的所有代码都在主线程中执行。

所以你应该能够做到这一点：

class GenericWorker(QObject):
    def __init__(self, function, *args, **kwargs):
        super(GenericWorker, self).__init__()

        self.function = function
        self.args = args
        self.kwargs = kwargs
        self.start.connect(self.run)

    start = pyqtSignal(str)

    @pyqtSlot
    def run(self, some_string_arg):
        self.function(*self.args, **self.kwargs)

my_thread = QThread()
my_thread.start()

# This causes my_worker.run() to eventually execute in my_thread:
my_worker = GenericWorker(...)
my_worker.moveToThread(my_thread)
my_worker.start.emit("hello")

另外，请仔细考虑当前丢弃的self.function结果会发生什么。您可以在GenericWorker上声明另一个信号，该信号接收结果，并且run()方法在完成后发出该信号，并将结果传递给它。

一旦你掌握了它并意识到你不应该并且不应该将QThread子类化，生活变得更加简单和容易。简单地说，永远不要在QThread中工作。你几乎不需要覆盖run。对于大多数用例，设置与QObject到QThread的正确关联并使用QT的信号/插槽创建了一种执行多线程编程的极其强大的方法。小心不要让你被推到工作线程的QObject徘徊......

http://ilearnstuff.blogspot.co.uk/2012/09/qthread-best-practices-when-qthread.html

Answer 2

我试图在我的应用程序中使用qris的示例，但一直在我的主线程中运行我的代码！这是他声称要调用的信号的运行方式！

基本上，当你在对象的构造函数中连接它时，连接将存在于主线程中的两个对象之间 - 因为QObject的属性属于创建它们的线程。当您将QObject移动到新线程时，连接不会随您移动。拿走将信号连接到run函数的行，并在将worker移动到新线程后将连接起来！

qris回答的相关变化：

class GenericWorker(QObject):
    def __init__(self, function, *args, **kwargs):
        super(GenericWorker, self).__init__()

        self.function = function
        self.args = args
        self.kwargs = kwargs

    start = pyqtSignal(str)

    @pyqtSlot
    def run(self, some_string_arg):
        self.function(*self.args, **self.kwargs)

my_thread = QThread()
my_thread.start()

# This causes my_worker.run() to eventually execute in my_thread:
my_worker = GenericWorker(...)
my_worker.moveToThread(my_thread)
my_worker.start.connect(my_worker.run) #  <---- Like this instead 
my_worker.start.emit("hello")

Answer 3

我已经尝试了@qris和@MatthewRunchey方法。

使用，@pyqtSlot装饰器Qt在发出信号时检查工作程序实例的“位置”：即使连接是在moveToThread之后发出信号之后进行的moveToThread执行工作线程中的插槽。

没有，@pyqtSlot装饰器Qt在建立连接的那一刻冻结工作实例的“位置”：如果它在moveToThread之前，则绑定到主线程，即使在moveToThread调用之后发出信号，插槽代码仍在主线程中执行。

在之后 moveToThread建立的连接在两种情况下都将要执行的工作线程绑定到插槽。

代码：

from PyQt5.QtCore import (QCoreApplication, QObject, QRunnable, QThread,
                          QThreadPool, pyqtSignal, pyqtSlot)

class Worker(QObject):
    def __init__(self):
        super(Worker, self).__init__()
#        self.call_f1.connect(self.f1)
#        self.call_f2.connect(self.f2)

    call_f1 = pyqtSignal()
    call_f2 = pyqtSignal()

    @pyqtSlot()
    def f1(self):
        print('f1', threading.get_ident())

    @pyqtSlot()
    def f2(self):
        print('f2', threading.get_ident())

app = QCoreApplication([])
print('main', threading.get_ident())
my_thread = QThread()
my_thread.start()

my_worker = Worker()
my_worker.call_f1.connect(my_worker.f1)
my_worker.call_f1.emit()
my_worker.moveToThread(my_thread)
my_worker.call_f2.connect(my_worker.f2)
my_worker.call_f1.emit()
my_worker.call_f2.emit()
sys.exit(app.exec_())

带有装饰器：

没有装饰器：

main 5520
f1 5520
f1 5520
f2 11472

在工作线程__init__中进行PS连接显然等效于在主线程中在moveToThread之前进行连接。

（在PyQt5，win64下测试）。

如何在pyqt中使用moveToThread（）正确使用QThread？

3 个答案: