PySide: Threading causes GUI to crash - multithreading

Question

I'm trying to learn the basics of threading with PySide, and so put together the below code. What I'm trying to do is launch a thread that will update a QPlainTextEdit widget using a list of string, with a delay between each string. Instead what I'm getting is a crash to desktop, and I can't understand why:
import sys
import time
from PySide import QtCore, QtGui
class Worker(QtCore.QThread):
to_log = QtCore.Signal(str)
def __init__(self, txt, parent=None):
super(Worker, self).__init__(parent)
self.txt = txt
def run(self):
for i in self.txt:
self.to_log.emit(i)
time.sleep(1)
class TestThreadsApp(QtGui.QWidget):
def __init__(self):
super(TestThreadsApp, self).__init__()
self.initUI()
def initUI(self):
self.log = QtGui.QPlainTextEdit()
self.pb = QtGui.QPushButton('Go')
hbox = QtGui.QHBoxLayout()
hbox.addWidget(self.log)
hbox.addWidget(self.pb)
self.setLayout(hbox)
self.setGeometry(300, 300, 300, 150)
self.setWindowTitle('Test')
self.show()
self.pb.clicked.connect(self.get_worker)
def get_worker(self):
self.proceed = False
worker = Worker(['This is a test', 'to understand threading'])
worker.to_log.connect(self.to_log)
worker.start()
def to_log(self, txt):
self.log.appendPlainText(txt)
def main():
app = QtGui.QApplication(sys.argv)
ex = TestThreadsApp()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
If I update the get_worker() method to the below, it will run, but the QPlainTextEdit widget is updated with all the strings simultaneously, where as the behavior I'm wanting is for the widget to be updated by the threaded processes as each string is emitted - not altogether after both have been emitted:
def get_worker(self):
self.proceed = False
worker = Worker(['This is a test', 'to understand threading'])
worker.to_log.connect(self.to_log)
worker.start()
while not worker.isFinished():
pass

Answer 1

You need to keep a reference to the thread, otherwise it will be garbage-collected as soon as get_worker returns.
So do something like this, instead:
def get_worker(self):
self.worker = Worker(['This is a test', 'to understand threading'])
self.worker.to_log.connect(self.to_log)
self.worker.start()