python - 用于对抗 "Not Responding"阻塞的多处理 GUI 模式

Question

创建多处理/GUI 编码系统的最佳方法是什么？

我想为互联网社区创建一个地方，让他们可以找到有关如何使用 multiprocessing 的示例。 python中的模块。

我看过几个multiprocessing的小例子在互联网上处理在主模块中调用的简单全局函数，但我发现这很少能轻易转化为任何人在 GUI 方面实际所做的任何事情。我认为许多程序会有他们想在单独的进程中使用的函数作为对象的方法(可能是其他对象的集合等)，也许单个 GUI 元素会有一个关联的对象需要调用它流程等

例如，我有一个相对复杂的程序，并且在为其获取响应式 GUI 时遇到问题，我认为这是由于我对 multiprocessing 缺乏理解所致。和线程 QThread .但是，我确实知道下面给出的示例至少会以我希望的方式在进程之间传递信息(由于能够执行 print 语句)，但我的 GUI 仍处于锁定状态。有谁知道这可能是什么原因造成的，如果我对多线程/多处理架构缺乏了解，这是否仍然是一个问题？

这是我正在做的一个小伪代码示例:

class Worker:
    ...
    def processing(self, queue):
        # put stuff into queue in a loop

# This thread gets data from Worker
class Worker_thread(QThread):
    def __init__(self):
        ...
        # make process with Worker inside
    def start_processing(self):
        # continuously get data from Worker
        # send data to Tab object with signals/slots

class Tab(QTabWidget):
    # spawn a thread separate from main GUI thread

    # update GUI using slot
    def update_GUI()

这段代码是完全可编译的示例，它体现了我程序的上层结构:

from PyQt4 import QtCore, QtGui
import multiprocessing as mp
import numpy as np
import sys
import time

# This object can hold several properties which will be used for the processing
# and will be run in the background, while it updates a thread with all of it's progress
class Worker:
    def __init__(self, some_var):
        self.some_var = some_var
        self.iteration = 0

    def some_complex_processing(self, queue):
        for i in range(0,5000):
            self.iteration += 1
            queue.put(self.iteration)
        queue.put('done with processing')

# This Woker_thread is a thread which will spawn a separate process (Worker).
# This separate is needed in order to separate the data retrieval
# from the main GUI thread, which should only quickly update when needed 
class Worker_thread(QtCore.QThread):
    # signals and slots are used to communicate back to the main GUI thread
    update_signal = QtCore.pyqtSignal(int)
    done_signal = QtCore.pyqtSignal()

    def __init__(self, parent, worker):
        QtCore.QThread.__init__(self, parent)
        self.queue = mp.Queue()
        self.worker = worker
        self.parent = parent
        self.process = mp.Process(target=self.worker.some_complex_processing, args=(self.queue,))

    # When the process button is pressed, this function will start getting data from Worker
    # this data is then retrieved by the queue and pushed through a signal
    # to Tab.update_GUI
    @QtCore.pyqtSlot()
    def start_computation(self):
        self.process.start()
        while(True):
            try:
                message = self.queue.get()
                self.update_signal.emit(message)
            except EOFError:
                pass
            if message == 'done with processing':
                self.done_signal.emit()
                break
            #self.parent.update_GUI(message)
        self.process.join()
        return

# Each tab will start it's own thread, which will spawn a process
class Tab(QtGui.QTabWidget):
    start_comp = QtCore.pyqtSignal()
    def __init__(self, parent, this_worker):
        self.parent = parent
        self.this_worker = this_worker
        QtGui.QTabWidget.__init__(self, parent)

        self.treeWidget = QtGui.QTreeWidget(self)
        self.properties = QtGui.QTreeWidgetItem(self.treeWidget, ["Properties"])
        self.step = QtGui.QTreeWidgetItem(self.properties, ["Iteration #"])

        self.thread = Worker_thread(parent=self, worker=self.this_worker)
        self.thread.update_signal.connect(self.update_GUI)
        self.thread.done_signal.connect(self.thread.quit)
        self.start_comp.connect(self.thread.start_computation)
        self.thread.start()

    ###############################
    # Here is what should update the GUI at every iteration of Worker.some_complex_processing()
    # The message appears to be getting sent, due to seeing the print statement in the console, but the GUI is not updated.
    @QtCore.pyqtSlot(int)
    def update_GUI(self, iteration):
        self.step.setText(0, str(iteration))
        #time.sleep(0.1)
        print iteration

    def start_signal_emit(self):
        self.start_comp.emit()

# GUI stuff
class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent = None):
        QtGui.QMainWindow.__init__(self)
        self.tab_list = []
        self.setTabShape(QtGui.QTabWidget.Rounded)
        self.centralwidget = QtGui.QWidget(self)
        self.top_level_layout = QtGui.QGridLayout(self.centralwidget)

        self.tabWidget = QtGui.QTabWidget(self.centralwidget)
        self.top_level_layout.addWidget(self.tabWidget, 1, 0, 25, 25)

        process_button = QtGui.QPushButton("Process")
        self.top_level_layout.addWidget(process_button, 0, 1)
        QtCore.QObject.connect(process_button, QtCore.SIGNAL("clicked()"), self.process)

        self.setCentralWidget(self.centralwidget)
        self.centralwidget.setLayout(self.top_level_layout)

        # Make Tabs in loop from button
        for i in range(0,10):
            name = 'tab' + str(i)
            self.tab_list.append(Tab(self.tabWidget, Worker(name)))
            self.tabWidget.addTab(self.tab_list[-1], name)

    # Do the processing
    def process(self):
        for tab in self.tab_list:
            tab.start_signal_emit()
        return

if __name__ == "__main__":
    app = QtGui.QApplication([])
    win = MainWindow()
    win.show()
    sys.exit(app.exec_())

更多信息:我正在编写一个程序，我想从中生成多个进程，并让它们在整个处理过程中不断显示它们的进度。我希望该程序能够进行多进程处理，以便尽可能地从程序中获得最佳速度。

目前，我正在尝试使用线程来生成进程并使用信号和槽来更新 GUI，同时队列不断检索数据。看来 queues , signals , 和 slots使用 print 时工作语句，但不能更新 GUI。如果有人对我应该如何构建它以使程序更易于管理有任何其他建议，我想学习。

编辑:我已经对 Min Lin 提出的调整进行了调整，并添加了 Worker一个QObject这样moveToThread()会工作。
这是我目前的新代码:

from PyQt4 import QtCore, QtGui
import multiprocessing as mp
import numpy as np
import sys
import time

class Worker(QtCore.QObject):
    update_signal = QtCore.pyqtSignal(int)
    done_signal = QtCore.pyqtSignal()

    def __init__(self, some_var):
        QtCore.QObject.__init__(self, parent=None)
        self.some_var = some_var
        self.iteration = 0
        self.queue = mp.Queue()
        self.process = mp.Process(target=self.some_complex_processing, args=(self.queue,))

    def some_complex_processing(self, queue):
        for i in range(0,5000):
            self.iteration += 1
            queue.put(self.iteration)
        queue.put('done with processing')

    @QtCore.pyqtSlot()
    def start_computation(self):
        self.process.start()
        while(True):
            try:
                message = self.queue.get()
                self.update_signal.emit(message)
            except EOFError:
                pass
            if message == 'done with processing':
                self.done_signal.emit()
                break
        self.process.join()
        return



class Tab(QtGui.QTabWidget):
    start_comp = QtCore.pyqtSignal()
    def __init__(self, parent, this_worker):
        self.parent = parent
        self.this_worker = this_worker
        QtGui.QTabWidget.__init__(self, parent)

        self.treeWidget = QtGui.QTreeWidget(self)
        self.properties = QtGui.QTreeWidgetItem(self.treeWidget, ["Properties"])
        self.step = QtGui.QTreeWidgetItem(self.properties, ["Iteration #"])

        # Use QThread is enough
        self.thread = QtCore.QThread();
        # Change the thread affinity of worker to self.thread.
        self.this_worker.moveToThread(self.thread);
        self.this_worker.update_signal.connect(self.update_GUI)
        self.this_worker.done_signal.connect(self.thread.quit)
        self.start_comp.connect(self.this_worker.start_computation)
        self.thread.start()

    ###############################
    # Here is what should update the GUI at every iteration of Worker.some_complex_processing()
    # The message appears to be getting sent, due to seeing the print statement in the console, but the GUI is not updated.
    @QtCore.pyqtSlot(int)
    def update_GUI(self, iteration):
        self.step.setText(0, str(iteration))
        #time.sleep(0.1)
        print iteration

    def start_signal_emit(self):
        self.start_comp.emit()

# GUI stuff
class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent = None):
        QtGui.QMainWindow.__init__(self)
        self.tab_list = []
        self.setTabShape(QtGui.QTabWidget.Rounded)
        self.centralwidget = QtGui.QWidget(self)
        self.top_level_layout = QtGui.QGridLayout(self.centralwidget)

        self.tabWidget = QtGui.QTabWidget(self.centralwidget)
        self.top_level_layout.addWidget(self.tabWidget, 1, 0, 25, 25)

        process_button = QtGui.QPushButton("Process")
        self.top_level_layout.addWidget(process_button, 0, 1)
        QtCore.QObject.connect(process_button, QtCore.SIGNAL("clicked()"), self.process)

        self.setCentralWidget(self.centralwidget)
        self.centralwidget.setLayout(self.top_level_layout)

        # Make Tabs in loop from button
        for i in range(0,10):
            name = 'tab' + str(i)
            self.tab_list.append(Tab(self.tabWidget, Worker(name)))
            self.tabWidget.addTab(self.tab_list[-1], name)

    # Do the processing
    def process(self):
        for tab in self.tab_list:
            tab.start_signal_emit()
        return

if __name__ == "__main__":
    app = QtGui.QApplication([])
    win = MainWindow()
    win.show()
    sys.exit(app.exec_())

感谢您提供的所有答案，我很欣赏每个人在描述他们认为是解决方案的想法时所做的详细程度，但不幸的是，我还无法执行这些类型的流程在 GUI 上显示对象的属性时，它们所属的对象。
然而，我从这篇文章中学到了很多东西，这让我意识到我目前拥有的线程版本正在挂起 GUI，因为 GUI 更新功能太大并且需要太多处理。

所以，我选择了QTimer()接近我的多线程版本，它的性能要好得多!我会建议任何面临类似问题的人至少尝试类似的事情。

我不知道这种解决 GUI 更新问题的方法，现在它是对我面临的问题的伪或临时修复。

Answer 1

GUI 应用程序非常适合测试东西，因为它很容易产生新任务并可视化正在发生的事情，所以我写了一个小示例应用程序(Screenshot，代码在下面)因为我确实想学习它为了我自己。

起初，我采用了与您类似的方法，尝试实现消费者/生产者模式，我在后台进程中苦苦挣扎，不断循环等待新工作，并为自己来回沟通。然后我发现了 Pool界面，然后我可以用几行代码替换所有那些丑陋的代码。您只需要一个池和一些回调:

#!/usr/bin/env python3
import multiprocessing, time, random, sys
from PySide.QtCore import * # equivalent: from PyQt4.QtCore import *
from PySide.QtGui import *   # equivalent: from PyQt4.QtGui import *

def compute(num):
    print("worker() started at %d" % num)
    random_number = random.randint(1, 6)
    if random_number in (2, 4, 6):
        raise Exception('Random Exception in _%d' % num)
    time.sleep(random_number)
    return num

class MainWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        self.toolBar = self.addToolBar("Toolbar")
        self.toolBar.addAction(QAction('Add Task', self, triggered=self.addTask))
        self.list = QListWidget()
        self.setCentralWidget(self.list)

        # Pool of Background Processes
        self.pool = multiprocessing.Pool(processes=4)

    def addTask(self):
        num_row = self.list.count()
        self.pool.apply_async(func=compute, args=(num_row,), callback=self.receiveResult,
                              error_callback=self.receiveException)
        item = QListWidgetItem("item %d" % num_row)
        item.setForeground(Qt.gray)
        self.list.addItem(item)

    def receiveResult(self, result):
        assert isinstance(result, int)
        print("end_work(), where result is %s" % result)
        self.list.item(result).setForeground(Qt.darkGreen)

    def receiveException(self, exception):
        error = str(exception)
        _pos = error.find('_') + 1
        num_row = int(error[_pos:])
        item = self.list.item(num_row)
        item.setForeground(Qt.darkRed)
        item.setText(item.text() + ' Retry...')
        self.pool.apply_async(func=compute, args=(num_row,), callback=self.receiveResult,
                              error_callback=self.receiveException)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    main_window = MainWindow()
    main_window.show()
    sys.exit(app.exec_())

编辑:我做了另一个使用 QTimer 而不是回调的示例，定期检查队列中的条目，更新 QProgressBar:

#!/usr/bin/env python3
import multiprocessing, multiprocessing.pool, time, random, sys
from PySide.QtCore import *
from PySide.QtGui import *

def compute(num_row):
    print("worker started at %d" % num_row)
    random_number = random.randint(1, 10)
    for second in range(random_number):
        progress = float(second) / float(random_number) * 100
        compute.queue.put((num_row, progress,))
        time.sleep(1)
    compute.queue.put((num_row, 100))

def pool_init(queue):
    # see http://stackoverflow.com/a/3843313/852994
    compute.queue = queue

class MainWindow(QMainWindow):
    def __init__(self):
        QMainWindow.__init__(self)
        self.toolBar = self.addToolBar("Toolbar")
        self.toolBar.addAction(QAction('Add Task', self, triggered=self.addTask))
        self.table = QTableWidget()
        self.table.verticalHeader().hide()
        self.table.setColumnCount(2)
        self.setCentralWidget(self.table)

        # Pool of Background Processes
        self.queue = multiprocessing.Queue()
        self.pool = multiprocessing.Pool(processes=4, initializer=pool_init, initargs=(self.queue,))

        # Check for progress periodically
        self.timer = QTimer()
        self.timer.timeout.connect(self.updateProgress)
        self.timer.start(2000)

    def addTask(self):
        num_row = self.table.rowCount()
        self.pool.apply_async(func=compute, args=(num_row,))
        label = QLabel("Queued")
        bar = QProgressBar()
        bar.setValue(0)
        self.table.setRowCount(num_row + 1)
        self.table.setCellWidget(num_row, 0, label)
        self.table.setCellWidget(num_row, 1, bar)

    def updateProgress(self):
        if self.queue.empty(): return
        num_row, progress = self.queue.get() # unpack
        print("received progress of %s at %s" % (progress, num_row))
        label = self.table.cellWidget(num_row, 0)
        bar = self.table.cellWidget(num_row, 1)
        bar.setValue(progress)
        if progress == 100:
            label.setText('Finished')
        elif label.text() == 'Queued':
            label.setText('Downloading')
        self.updateProgress() # recursion

if __name__ == '__main__':
    app = QApplication(sys.argv)
    main_window = MainWindow()
    main_window.show()
    sys.exit(app.exec_())