Question

我决定在我的一个脚本中添加一个GUI。该脚本是一个简单的Web scraper。我决定使用工作线程作为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，我决定它应该等到QLineEdit触发returnPressed，然后将其内容发送到工作线程，以便它可以发送它用于验证。这应该比忙碌更好 - 等待按下返回键。

似乎等待信号并不像我想象的那样直截了当，在搜索了一段时间后，我遇到了几个类似于this的解决方案。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变得更加复杂。

经过几个小时的修补后，它仍然无效。

应该发生什么：

下载数据，直到参考验证码并进入循环
下载验证码并将其显示给用户，通过致电QEventLoop

self.loop.exec_()

在QEventLoop类

loop.quit()

self.line_edit.returnPressed.connect(self.worker.stop_waiting)

main_window

验证验证失败时验证验证码和循环，否则重试现在应该可下载的最后一个网址，然后继续使用下一个网址

会发生什么：

......见上文......
退出QEventLoop不起作用。调用self.loop.isRunning()后，False会返回exit()。 self.isRunning返回True，因此线程在奇怪的情况下似乎没有死亡。线程仍在self.loop.exec_()线停止。因此，即使事件循环告诉我它不再运行，线程也会执行事件循环。
GUI响应工作线程类的插槽。我可以看到文本beeing发送到工作线程，事件循环的状态和线程本身，但在上面提到的行被执行后没有任何内容。

代码有点复杂，因此我添加了一些伪代码-python-mix而忽略了不重要的内容：

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

您所描述的内容看起来非常适合QWaitCondition。

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_())

Answer 2

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

您需要将QObject移动到该线程并将其插槽连接到该信号，该插槽将在该线程内执行：

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()

PySide等待来自工作线程中主线程的信号

2 个答案: