ZetCode PyQt4 tutorial signals and slots

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

In this example, we connect a signal
of a QtGui.QSlider to a slot
of a QtGui.QLCDNumber. 

author: Jan Bodnar
website: zetcode.com
last edited: October 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):

        lcd = QtGui.QLCDNumber(self)
        sld = QtGui.QSlider(QtCore.Qt.Horizontal, self)

        vbox = QtGui.QVBoxLayout()
        vbox.addWidget(lcd)
        vbox.addWidget(sld)

        self.setLayout(vbox)
        # Here we connect a valueChanged signal of the slider to the display slot of the lcd number.
        # The sender is an object that sends a signal. The receiver is the object that receives the signal. The slot is the method that reacts to the signal.
        sld.valueChanged.connect(lcd.display)

        self.setGeometry(300, 300, 250, 150)
        self.setWindowTitle('Signal & slot')
        self.show()

def main():

    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

--------------------------------------------------------------------------------

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

In this example, we reimplement an
event handler. 

author: Jan Bodnar
website: zetcode.com
last edited: October 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QWidget):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):      

        self.setGeometry(300, 300, 250, 150)
        self.setWindowTitle('Event handler')
        self.show()

    # In our example, we reimplement the keyPressEvent() event handler.
    def keyPressEvent(self, e):

        # If we click the Escape button, the application terminates.
        if e.key() == QtCore.Qt.Key_Escape:
            self.close()

def main():

    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

--------------------------------------------------------------------------------

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial 

In this example, we determine the event sender
object.

author: Jan Bodnar
website: zetcode.com
last edited: October 2011
"""

import sys
from PyQt4 import QtGui, QtCore

class Example(QtGui.QMainWindow):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):      

        btn1 = QtGui.QPushButton("Button 1", self)
        btn1.move(30, 50)

        btn2 = QtGui.QPushButton("Button 2", self)
        btn2.move(150, 50)

        # Both buttons are connected to the same slot.
        btn1.clicked.connect(self.buttonClicked)
        btn2.clicked.connect(self.buttonClicked)

        self.statusBar()

        self.setGeometry(300, 300, 290, 150)
        self.setWindowTitle('Event sender')
        self.show()

    def buttonClicked(self):

        # We determine the signal source by calling the sender() method. In the statusbar of the application, we show the label of the button being pressed.
        sender = self.sender()
        self.statusBar().showMessage(sender.text() + ' was pressed')

def main():

    app = QtGui.QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

--------------------------------------------------------------------------------

#!/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):

    # A signal is created with the QtCore.pyqtSignal() as a class attribute of the external Communicate class.
    closeApp = QtCore.pyqtSignal() 

class Example(QtGui.QMainWindow):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):      

        # The custom closeApp signal is connected to the close() slot of the QtGui.QMainWindow.
        self.c = Communicate()
        self.c.closeApp.connect(self.close)       

        self.setGeometry(300, 300, 290, 150)
        self.setWindowTitle('Emit signal')
        self.show()

    # When we click on the window with a mouse pointer, the closeApp signal is emitted. The application terminates.
    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()