pyqt5 qthread-在另一个脚本中运行线程

Question

I found a usefull example where Qthread is used to operate multiple threads ( Pyqt5 qthread + signal not working + gui freeze foo ), but I'm iterested in running the thread in a different script file. I've devided the example into two files, MainThread.py and Subthread.py

MainThread.py

import sys

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

def trap_exc_during_debug(*args):
    # when app raises uncaught exception, print info
    print(args)


# install exception hook: without this, uncaught exception would cause application to exit
sys.excepthook = trap_exc_during_debug


class MyWidget(QWidget):
    NUM_THREADS = 5

    # sig_start = pyqtSignal()  # needed only due to PyCharm debugger bug (!)
    sig_abort_workers = pyqtSignal()

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

        self.setWindowTitle("Thread Example")
        form_layout = QVBoxLayout()
        self.setLayout(form_layout)
        self.resize(400, 800)

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

        self.button_stop_threads = QPushButton()
        self.button_stop_threads.clicked.connect(self.abort_workers)
        self.button_stop_threads.setText("Stop threads")
        self.button_stop_threads.setDisabled(True)
        form_layout.addWidget(self.button_stop_threads)

        self.log = QTextEdit()
        form_layout.addWidget(self.log)

        self.progress = QTextEdit()
        form_layout.addWidget(self.progress)

        QThread.currentThread().setObjectName('main')  # threads can be named, useful for log output
        self.__workers_done = None
        self.__threads = None

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

        self.__workers_done = 0
        self.__threads = []
        for idx in range(self.NUM_THREADS):
            worker = Worker(idx)
            thread = QThread()
            thread.setObjectName('thread_' + str(idx))
            self.__threads.append((thread, worker))  # need to store worker too otherwise will be gc'd
            worker.moveToThread(thread)

            # get progress messages from worker:
            worker.sig_step.connect(self.on_worker_step)
            worker.sig_done.connect(self.on_worker_done)
            worker.sig_msg.connect(self.log.append)

            # control worker:
            self.sig_abort_workers.connect(worker.abort)

            # get read to start worker:
            # self.sig_start.connect(worker.work)  # needed due to PyCharm debugger bug (!); comment out next line
            thread.started.connect(worker.work)
            thread.start()  # this will emit 'started' and start thread's event loop

        # self.sig_start.emit()  # needed due to PyCharm debugger bug (!)

    @pyqtSlot(int, str)
    def on_worker_step(self, worker_id: int, data: str):
        self.log.append('Worker #{}: {}'.format(worker_id, data))
        self.progress.append('{}: {}'.format(worker_id, data))

    @pyqtSlot(int)
    def on_worker_done(self, worker_id):
        self.log.append('worker #{} done'.format(worker_id))
        self.progress.append('-- Worker {} DONE'.format(worker_id))
        self.__workers_done += 1
        if self.__workers_done == self.NUM_THREADS:
            self.log.append('No more workers active')
            self.button_start_threads.setEnabled(True)
            self.button_stop_threads.setDisabled(True)
            # self.__threads = None

    @pyqtSlot()
    def abort_workers(self):
        self.sig_abort_workers.emit()
        self.log.append('Asking each worker to abort')
        for thread, worker in self.__threads:  # note nice unpacking by Python, avoids indexing
            thread.quit()  # this will quit **as soon as thread event loop unblocks**
            thread.wait()  # <- so you need to wait for it to *actually* quit

        # even though threads have exited, there may still be messages on the main thread's
        # queue (messages that threads emitted before the abort):
        self.log.append('All threads exited')


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

    form = MyWidget()
    form.show()

    sys.exit(app.exec_())

SubThread.py

import time


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



class Worker(QObject):
    """
    Must derive from QObject in order to emit signals, connect slots to other signals, and operate in a QThread.
    """

    sig_step = pyqtSignal(int, str)  # worker id, step description: emitted every step through work() loop
    sig_done = pyqtSignal(int)  # worker id: emitted at end of work()
    sig_msg = pyqtSignal(str)  # message to be shown to user

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

    @pyqtSlot()
    def work(self):
        """
        Pretend this worker method does work that takes a long time. During this time, the thread's
        event loop is blocked, except if the application's processEvents() is called: this gives every
        thread (incl. main) a chance to process events, which in this sample means processing signals
        received from GUI (such as abort).
        """
        thread_name = QThread.currentThread().objectName()
        thread_id = int(QThread.currentThreadId())  # cast to int() is necessary
        self.sig_msg.emit('Running worker #{} from thread "{}" (#{})'.format(self.__id, thread_name, thread_id))

        for step in range(100):
            time.sleep(0.1)
            self.sig_step.emit(self.__id, 'step ' + str(step))

            # check if we need to abort the loop; need to process events to receive signals;
            app.processEvents()  # this could cause change to self.__abort
            if self.__abort:
                # note that "step" value will not necessarily be same for every thread
                self.sig_msg.emit('Worker #{} aborting work at step {}'.format(self.__id, step))
                break

        self.sig_done.emit(self.__id)

    def abort(self):
        self.sig_msg.emit('Worker #{} notified to abort'.format(self.__id))
        self.__abort = True

The problem is that app.processEvents is now in the SubThread script, meaning that abort can't be used. Is there a way to apply processEvents in a correct way?

The reason for a separated thread script is in the future to run complex measuring procedures and timers and to keep the main file readable

Answer 1

Just call QCoreApplication.processEvents() instead. This is a static method (so can be called on the class rather than an instance) and processes events for the event loop of the calling thread.

Edit: This is described in the C++ documentation , which translates well to Python