如何在非主线程 QObject 中开始工作

Question

根据 Qt 文档和网络上的其他示例，我认为以下使用 QThread.started 信号的程序会在 non 启动工作程序-主线程。但事实并非如此，而是从 main 线程调用每个 work 槽：

import time
import sys

from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot
from PyQt5.QtWidgets import QApplication, QPushButton, QTextEdit, QVBoxLayout, QWidget


def trap_exc_during_debug(*args):
    # when app exits, put breakpoint in next line when run in debugger, and analyse args
    pass


sys.excepthook = trap_exc_during_debug


class Checker(QObject):
    sig_step = pyqtSignal(int, str)
    sig_done = pyqtSignal(int)

    def __init__(self, id: int):
        super().__init__()
        self.__id = id

    @pyqtSlot()
    def work(self):
        thread_name = QThread.currentThread().objectName()
        thread_id = int(QThread.currentThreadId())
        print('running work #{} from thread "{}" (#{})'.format(self.__id, thread_name, thread_id))

        time.sleep(2)
        self.sig_step.emit(self.__id, 'step 1')
        time.sleep(2)
        self.sig_step.emit(self.__id, 'step 2')
        time.sleep(2)
        self.sig_done.emit(self.__id)


class MyWidget(QWidget):
    NUM_THREADS = 3

    sig_start = pyqtSignal()

    def __init__(self):
        super().__init__()

        self.setWindowTitle("Thread Example")
        form_layout = QVBoxLayout()
        self.setLayout(form_layout)
        self.resize(200, 200)

        self.push_button = QPushButton()
        self.push_button.clicked.connect(self.start_threads)
        self.push_button.setText("Start {} threads".format(self.NUM_THREADS))
        form_layout.addWidget(self.push_button)

        self.log = QTextEdit()
        form_layout.addWidget(self.log)
        # self.log.setMaximumSize(QSize(200, 80))

        self.text_edit = QTextEdit()
        form_layout.addWidget(self.text_edit)
        # self.text_edit.setMaximumSize(QSize(200, 60))

        QThread.currentThread().setObjectName('main')
        self.__threads_done = None
        self.__threads = None

    def start_threads(self):
        self.log.append('starting {} threads'.format(self.NUM_THREADS))
        self.push_button.setDisabled(True)

        self.__threads_done = 0
        self.__threads = []
        for idx in range(self.NUM_THREADS):
            checker = Checker(idx)
            thread = QThread()
            thread.setObjectName('thread_' + str(idx))
            self.__threads.append((thread, checker))  # need to store checker too otherwise will be gc'd
            checker.moveToThread(thread)
            checker.sig_step.connect(self.on_thread_step)
            checker.sig_done.connect(self.on_thread_done)

            # self.sig_start.connect(checker.work)  # method 1 works: each work() is in non-main thread
            thread.started.connect(checker.work)  # method 2 doesn't work: each work() is in main thread
            thread.start()

        self.sig_start.emit()  # this is only useful in method 1

    @pyqtSlot(int, str)
    def on_thread_step(self, thread_id, data):
        self.log.append('thread #{}: {}'.format(thread_id, data))
        self.text_edit.append('{}: {}'.format(thread_id, data))

    @pyqtSlot(int)
    def on_thread_done(self, thread_id):
        self.log.append('thread #{} done'.format(thread_id))
        self.text_edit.append('-- Thread {} DONE'.format(thread_id))
        self.__threads_done += 1
        if self.__threads_done == self.NUM_THREADS:
            self.log.append('No more threads')
            self.push_button.setEnabled(True)


if __name__ == "__main__":
    app = QApplication([])

    form = MyWidget()
    form.show()

    sys.exit(app.exec_())

如果我改用自定义信号，效果很好。要查看此内容，请注释掉 "method 2" 行并取消注释 "method 1" 行并重复运行。

如果不用创建自定义信号就可以启动 worker 肯定会更好，有没有办法做到这一点（同时坚持对 worker 调用 moveToThread 的设计）？

注意：QThread.started 信号的文档帮助不大：

This signal is emitted from the associated thread when it starts executing

对我来说，这意味着 started 将在非主线程中发出，这样它所连接的 work 插槽将在非主线程中被调用，但是这显然不是这样。即使我的解释不正确并且信号实际上是在主线程中发出的，两种方法的连接类型都是默认值 Qt.AutoConnection，到 QObject 移动到另一个线程，因此 started 信号应该异步传输（即通过每个检查器的 QThread 事件循环），显然不是这种情况。

Answer 1

我向 jetbrains 发布了支持请求，他们迅速回复：

It was made intentionally for a better debugging. You can uncheck setting Settings | Build, Execution, Deployment | Python Debugger > PyQt compatible and will have workers started as expected.

太棒了！

如何在非主线程 QObject 中开始工作

How to start work in a non-main-thread QObject

python

pyqt

pyqt5

signals-slots

qthread