Example of using worker QThreads to process data before loading web results. (pyside, qt)

web_threads.py

from PySide import QtCore, QtGui, QtWebKit
from threading import current_thread


class MainWindow(QtGui.QMainWindow):

	def __init__(self):
		super(MainWindow, self).__init__()
		
		container = QtGui.QWidget(self)

		self._tab = QtGui.QTabWidget(container)
		self._button = QtGui.QPushButton("New", container)

		layout = QtGui.QVBoxLayout(container)
		layout.setContentsMargins(4,4,4,4)
		layout.addWidget(self._tab)
		layout.addWidget(self._button)

		self.setCentralWidget(container)

		self._button.clicked.connect(self.newPage)

	def newPage(self):
		page = BrowserPage(self._tab)
		self._tab.addTab(page, "Page %d" % self._tab.count())
		page.start()


class BrowserPage(QtGui.QFrame):
	"""
	A web page view that will do long-running work in a thread, 
	and then load the results when ready. 
	"""
	loadStarted = QtCore.Signal()
	loadFinished = QtCore.Signal()

	def __init__(self, parent=None):
		super(BrowserPage, self).__init__(parent)
		self.__thread = None 
		self.__loader = None

		self.__view = QtWebKit.QWebView(self)
		self.__stat = QtGui.QStatusBar(self)
		self.__stat.setSizeGripEnabled(False)
		self.__stat.setFixedHeight(22)

		layout = QtGui.QVBoxLayout(self)
		layout.setContentsMargins(0,0,0,0)
		layout.setSpacing(0)
		layout.addWidget(self.__view)
		layout.addWidget(self.__stat)

	def start(self):
		if self.__thread is not None:
			return

		thread = QtCore.QThread()
		loader = PageLoader()
		loader.moveToThread(thread)

		thread.started.connect(loader.load)
		thread.finished.connect(self.__finished)

		loader.progress.connect(self.__updateProgress)
		loader.finished.connect(self.__view.load)
		loader.finished.connect(thread.quit)

		self.__thread = thread 
		self.__loader = loader

		self.loadStarted.emit()
		self.__stat.showMessage("Starting to load...")
		thread.start()

	def __updateProgress(self, prog):
		self.__stat.showMessage("Loaded {:.1%}".format(prog))

	def __finished(self):
		self.__stat.clearMessage()
		self.loadFinished.emit()
		self.__thread.deleteLater()
		self.__loader.deleteLater()
		self.__thread = None 
		self.__loader = None


class PageLoader(QtCore.QObject):
	"""
	Provides the logic for processing web content concurrently, 
	and emitting results when ready.
	"""
	progress = QtCore.Signal(float)
	finished = QtCore.Signal(QtCore.QUrl)

	def load(self):
		tid = current_thread().ident
		num = 5
		for i in xrange(1, num+1):
			print "(Thread: %d) Loading %d/%d ..." % (tid, i, num)
			QtCore.QThread.sleep(1)
			self.progress.emit(i/float(num))

		url = QtCore.QUrl("http://www.google.com")
		self.finished.emit(url)



if __name__ == "__main__":
	app = QtGui.QApplication([])
	w = MainWindow()
	w.resize(1024, 768)
	w.show()
	w.raise_()
	app.exec_()