I've encountered this problem twice now in subtle ways, I think this is
at the root of my last question about the QWebView; I've included sample
code this time to illustrate.
In the attached script, I have a widget class and a processor class.
The processor represents some kind of processing engine that's going to
do a lengthy multi-part routine of some kind. The widget class is the
gui for the engine.
The "go" button is connected to the "process" method of the processor
object. The process() method emits a signal with a string, does process
A for 10 seconds, emits a signal with a string, does process B for 10
seconds, and emits a final signal with a string.
The widget class is supposed to be picking up the signals and displaying
the strings. So the expected output is:
<click "go">
first message displays
<wait 10 seconds>
second message displays
<wait 10 seconds>
final message displays
The actual output is that nothing happens for 20 seconds, then all the
text displays. Because the widget isn't going to process any received
signals until the called method exits.
How do I produce the expected behavior here?
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
from time import sleep
class mywidget(QWidget):
def __init__(self):
super(QWidget, self).__init__()
self.gobutton = QPushButton("Go")
self.logwindow = QTextEdit()
self.setLayout(QVBoxLayout())
self.layout().addWidget(self.gobutton)
self.layout().addWidget(self.logwindow)
self.processor = processor()
self.connect(self.processor, SIGNAL("statusChanged(str)"), self.logwindow.append)
self.connect(self.gobutton, SIGNAL("clicked()"), self.processor.process)
class processor(QObject):
def __init__(self):
super(QObject, self).__init__()
def process(self):
self.emit (SIGNAL("statusChanged(str)"), "Starting A\n")
#simulating some lengthy process A
sleep(10)
self.emit (SIGNAL("statusChanged(str)"), "A done, starting B\n")
#simulating some lengthy process B
sleep(10)
self.emit (SIGNAL("statusChanged(str)"), "B done. Finished\n")
if __name__ == '__main__':
app = QApplication(sys.argv)
w = mywidget()
w.show()
app.exec_()
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