Objects created from a QtCore.QObject can emit signals. In the following example we will see how we can emit custom signals.
#!/usr/bin/python
# -*- coding: utf-8 -*-
"""
ZetCode PyQt4 tutorial
In this example, we show how to emit a
signal.
author: Jan Bodnar
website: zetcode.com
last edited: January 2015
"""
import sys
from PyQt4 import QtGui, QtCore
class Communicate(QtCore.QObject):
closeApp = QtCore.pyqtSignal()
class Example(QtGui.QMainWindow):
def __init__(self):
super(Example, self).__init__()
self.initUI()
def initUI(self):
self.c = Communicate()
self.c.closeApp.connect(self.close)
self.setGeometry(300, 300, 290, 150)
self.setWindowTitle('Emit signal')
self.show()
def mousePressEvent(self, event):
self.c.closeApp.emit()
def main():
app = QtGui.QApplication(sys.argv)
ex = Example()
sys.exit(app.exec_())
if __name__ == '__main__':
main()
We create a new signal called closeApp. This signal is emitted during a mouse press event. The signal is connected to the close() slot of the QtGui.QMainWindow.
class Communicate(QtCore.QObject):
closeApp = QtCore.pyqtSignal()
A signal is created with the QtCore.pyqtSignal() as a class attribute of the external Communicate class.
self.c.closeApp.connect(self.close)
The custom closeApp signal is connected to the close() slot of the QtGui.QMainWindow.
def mousePressEvent(self, event):
self.c.closeApp.emit()
When we click on the window with a mouse pointer, the closeApp signal is emitted. The application terminates.