from PyQt4.QtCore import *
from PyQt4.QtGui import *
import sys

class dlgTest( QDialog ):
	def __init__( self, parent = None ):
		QDialog.__init__( self, parent )
		
		self.mainLayout = QVBoxLayout()
		
		self.btnStart = QPushButton()
		self.btnStart.setText("Start")
		QObject.connect( self.btnStart, SIGNAL( "clicked()" ), self.startCalculation )
		
		self.btnStop = QPushButton()
		self.btnStop.setText("Stop")
		QObject.connect( self.btnStop, SIGNAL( "clicked()" ), self.stopCalculation )
		
		self.lblProgress = QLabel()
		self.lblProgress.setText("Progress: 0")
		
		self.mainLayout.addWidget(self.btnStart)
		self.mainLayout.addWidget(self.btnStop)
		self.mainLayout.addWidget(self.lblProgress)
		self.setLayout(self.mainLayout)
		
		self.setWindowTitle( self.tr( "Thread" ) )
		self.resize( 120, 100 )
	
	# запуск "анализа" в отдельном потоке
	def startCalculation( self ):
		self.threadCalc = workThread()
		QObject.connect( self.threadCalc, SIGNAL( "runStatus(PyQt_PyObject)" ), self.runStatusFromThread )
		self.threadCalc.start()
	# остановка "анализа" по нажатию на кнопку
	def stopCalculation( self ):
		self.threadCalc.stop()
	# для отображения процесса выполнения
	def runStatusFromThread( self, status ):
		self.lblProgress.setText( "Progress: " + str( status ) )

class workThread( QThread ):
	def __init__( self, parent = None ):
		QThread.__init__( self, parent )
		self.running = False
		self.counter = 0
	
	def run( self ):
		self.running = True
		while True:
			self.counter += 1
			self.emit( SIGNAL( "runStatus(PyQt_PyObject)" ), self.counter )
			self.sleep(1)
	# остановка потока
	def stop( self ):
		#self.counter = 0
		self.running = False

if __name__ == "__main__":
	app = QApplication( sys.argv )
	frm = dlgTest()
	frm.show()
	sys.exit( app.exec_() )

class workThread( QThread ):
       ...
	
	def run( self ):
		self.running = True
		while self.running:
			self.counter += 1
			self.emit( SIGNAL( "runStatus(PyQt_PyObject)" ), self.counter )
			self.sleep(1)

# остановка потока
    def stop( self ):
        print 'stop'
        self.terminate()
        self.wait()

class StopException(Exception): pass

class Handler(object):
    'Типа хендлер'
    def __init__(self, processor):
        self.processor = processor

    def start(self, id):
        self.id = id

    def work_start(self):
        'Начало части алгоритма'
        pass
    def work_pass(self, curr):
        self.processor.setProgress(curr)
    def work_error(self, exc):
        self.processor.process_stop()
        raise StopException, exc
    def work_end(self):
        'Конец части алгоритма'
        pass

    def end(self):
        pass
    def stop(self):
        pass


def work(work_data, handler):
    'Какая-то абстрактная работа'
    id = get_id()
    handler.start(id)

    try:
        self.work_start()
        for i in range(100):
            try:
                # Пашем...
                handler.work_pass(i)
            except Error, exc:
                # Ууупс
                handler.work_error(exc)
        self.work_end()

    except StopException, exc:
        handler.stop(exc)
        return

    handler.end()

# Используется примерно так.
handler = Handler(processor)
work(data, handler)