PySide等待来自工作线程中主线程的信号

Question

我决定在我的一个脚本中添加一个GUI。脚本是一个简单的web刮刀。我决定使用一个工作线程来下载和解析数据可能需要一段时间。我决定使用PySide，但我对Qt的总体了解非常有限。

由于脚本应该在遇到验证码时等待用户输入，所以我决定应该等到QLineEdit触发returnPressed，然后将其内容发送到工作线程，以便它可以发送验证。这应该比忙着等待按下返回键要好。

似乎等待信号并不像我想象的那么直接，经过一段时间的搜索，我发现了几个类似于this的解决方案。不过，跨线程的信令和工作线程中的本地事件循环使我的解决方案更加复杂。

修了几个小时后还是不行。

会发生什么：

• 下载数据直到被引用到验证码并进入循环
• 下载验证码并显示给用户，通过调用self.loop.exec_()启动QEventLoop
• 通过调用通过main_window类中的self.line_edit.returnPressed.connect(self.worker.stop_waiting)连接的工作线程槽中的QEventLoop退出loop.quit()
• 验证验证码并循环如果验证失败，否则重试最后一个现在应该可以下载的url，然后继续下一个url

会发生什么：

• ……见上图。。。

• 退出QEventLoop不起作用。self.loop.isRunning()调用其exit()后返回False。self.isRunning返回True，因此线程似乎没有在奇怪的情况下死亡。但线程仍然停留在self.loop.exec_()行。因此，即使事件循环告诉我它不再运行，线程仍然无法执行事件循环。

• GUI的响应与worker线程类的插槽一样。我可以看到发送给工作线程的文本、事件循环的状态和线程本身，但在执行上述行之后什么也看不到。

代码有点复杂，因此我添加了一点伪代码python mix，省去了不重要的：

class MainWindow(...):
    # couldn't find a way to send the text with the returnPressed signal, so I
    # added a helper signal, seems to work though. Doesn't work in the
    # constructor, might be a PySide bug?
    helper_signal = PySide.QtCore.Signal(str)
    def __init__(self):
        # ...setup...
        self.worker = WorkerThread()
        self.line_edit.returnPressed.connect(self.helper_slot)
        self.helper_signal.connect(self.worker.stop_waiting)

    @PySide.QtCore.Slot()
    def helper_slot(self):
        self.helper_signal.emit(self.line_edit.text())

class WorkerThread(PySide.QtCore.QThread):
    wait_for_input = PySide.QtCore.QEventLoop()

    def run(self):
        # ...download stuff...
        for url in list_of_stuff:
            self.results.append(get(url))

    @PySide.QtCore.Slot(str)
    def stop_waiting(self, text):
        self.solution = text
        # this definitely gets executed upon pressing return
        self.wait_for_input.exit()

    # a wrapper for requests.get to handle captcha
    def get(self, *args, **kwargs):
        result = requests.get(*args, **kwargs)
        while result.history: # redirect means captcha
            # ...parse and extract captcha...
            # ...display captcha to user via not shown signals to main thread...

            # wait until stop_waiting stops this event loop and as such the user
            # has entered something as a solution
            self.wait_for_input.exec_()

            # ...this part never get's executed, unless I remove the event
            # loop...

            post = { # ...whatever data necessary plus solution... }
            # send the solution
            result = requests.post('http://foo.foo/captcha_url'), data=post)
        # no captcha was there, return result
        return result

frame = MainWindow()
frame.show()
frame.worker.start()
app.exec_()

Answer 1

插槽在创建QThread的线程中执行，而不是在QThread控制的线程中执行。

您需要将QObject移动到线程并将其插槽连接到信号，该插槽将在线程内部执行：

class SignalReceiver(QtCore.QObject):
    def __init__(self):
        self.eventLoop = QEventLoop(self)             

    @PySide.QtCore.Slot(str)
    def stop_waiting(self, text):                   
        self.text = text
        eventLoop.exit()

    def wait_for_input(self):
        eventLoop.exec()
        return self.text

class MainWindow(...):
     ...
     def __init__(self):
        ...
        self.helper_signal.connect(self.worker.signalReceiver.stop_waiting)

class WorkerThread(PySide.QtCore.QThread): 
    def __init__(self):
        self.signalReceiver = SignalReceiver() 
        # After the following call the slots will be executed in the thread             
        self.signalReceiver.moveToThread(self)    

    def get(self,  *args, **kwargs):
        result = requests.get(*args, **kwargs)
        while result.history:
            ...
            self.result = self.signalReceiver.wait_for_input()   

Answer 2

你所描述的看起来很适合^{}。

简单示例：

import sys
from PySide import QtCore, QtGui

waitCondition = QtCore.QWaitCondition()
mutex = QtCore.QMutex()

class Main(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(Main, self).__init__()

        self.text = QtGui.QLineEdit()
        self.text.returnPressed.connect(self.wakeup)

        self.worker = Worker(self)
        self.worker.start()

        self.setCentralWidget(self.text)

    def wakeup(self):
        waitCondition.wakeAll()

class Worker(QtCore.QThread):
    def __init__(self, parent=None):
        super(Worker, self).__init__(parent)

    def run(self):
        print "initial stuff"

        mutex.lock()
        waitCondition.wait(mutex)
        mutex.unlock()

        print "after returnPressed"

if __name__=="__main__":      
    app = QtGui.QApplication(sys.argv)
    m = Main()
    m.show()
    sys.exit(app.exec_())