[PyQt] problem with qthread and signal/slot

[Phil Thompson]

On Saturday 14 April 2007 5:44 am, Pradnyesh Sawant wrote:
> Hello,
> i've written a small code which increments a counter in the backend,
> and prints it on the frontend. However, i'm passing a dummy string var
> along with it in the signal/slot mechanism. The problem is that from
> the 2nd call onwards, the string gets printed, but NOT in the 1st
> call. (eg, in the foll code i get:- 1, (2, 'a'), (3, 'a'), ...)
> The code is:-
> **************************************************
> import time
> import sys
> from PyQt4 import QtGui, QtCore
>
> class Counter(QtCore.QThread):
>     def __init__(self):
>         QtCore.QThread.__init__(self)
>         self.cntr = 0
>     def run(self):
>         while True:
>             self.cntr += 1
>             self.emit(QtCore.SIGNAL("showCntr"), (self.cntr, "a"))
>             time.sleep(1)
>             if self.cntr == 10: break
> class Gui(QtGui.QDialog):
>     def __init__(self, parent = None):
>         QtGui.QDialog.__init__(self, parent)
>         frameStyle = QtGui.QFrame.Sunken | QtGui.QFrame.Panel
>
>         self.lCntr = QtGui.QLabel()
>         self.lCntr.setFrameStyle(frameStyle)
>         loGrd = QtGui.QGridLayout()
>         loGrd.addWidget(self.lCntr, 0, 0)
>         self.setLayout(loGrd)
>         self.setWindowTitle(self.tr("Counter"))
>     def showCntr(self, val):
>         print val
>         self.lCntr.setText(str(val))
> if __name__ == "__main__":
>     app = QtGui.QApplication(sys.argv)
>     dialog = Gui()
>     cntr = Counter()
>     cntr.start()
>     QtCore.QObject.connect(cntr, QtCore.SIGNAL("showCntr"),
>             dialog.showCntr, QtCore.Qt.QueuedConnection)
>     sys.exit(dialog.exec_())
> **************************************************
> Also, this is my 1st ever prog with signals/slots across threads; and
> am a newbie to python and pyqt. So please be considerate and kind
> enough to point out mistakes/better approaches with the above code.
>
> Thanks a lot!

It works fine for me.

Phil