= Fading and unfading a widget with a delay =

On the !PyQt mailing list, [[http://www.riverbankcomputing.com/pipermail/pyqt/2009-November/025007.html|Tim and Alison Bentley]] asked for a way to produce a fade-unfade animation.

The following example code uses a single-shot QTimer to schedule the unfade step of the animation for one second after the fade occurs.

{{{
#!python
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Window(QWidget):

    def __init__(self, parent = None):
    
        QWidget.__init__(self, parent)
        
        button = QPushButton(self.tr("Click me!"))
        
        button.clicked.connect(self.fade)
        
        layout = QVBoxLayout(self)
        layout.addWidget(button)
    
    def fade(self):
    
        self.setWindowOpacity(0.5)
        QTimer.singleShot(1000, self.unfade)
    
    def unfade(self):
    
        self.setWindowOpacity(1)


if __name__ == "__main__":

    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())
}}}