How to inherit from QWidget in PyQt?

Question

Maigcally I can't inherit from QWidget using PyQt 4:

from PyQt4.QtGui import QApplication, QMainWindow, QWidget

class MyWidget(QWidget):
    pass

if __name__ == "__main__":
    app = QApplication([])
    window = QMainWindow()
    window.resize(200, 200)
    widget1 = MyWidget(window)
    widget1.resize(100, 100)
    widget1.setStyleSheet("background-color:#FFFFFF")
    window.show()
    app.exec_()

It doesn't work. I just can't see the widget. But, using QLabel instead of QWidget works.

Thanks.

Solution

Reimplement paintEvent:

class MyWidget(QWidget):
    def paintEvent(self, event):
        o = QStyleOption()
        o.initFrom(self)
        p = QPainter(self)
        self.style().drawPrimitive(QStyle.PE_Widget, o, p, self)  

Answer 1

You are subclassing correctly. The "problem" is just that the QWidget has the same background colour as the main window (your call to setStyleSheet is not working).

As proof, run this code from a terminal:

from PyQt4.QtGui import QApplication, QMainWindow, QWidget, QLabel

class MyWidget(QWidget):
     def enterEvent(self, evt):
        print 'a'

if __name__ == "__main__":
    app = QApplication([])
    window = QMainWindow()
    window.resize(200, 200)
    widget1 = MyWidget(window)
    widget1.resize(100, 100)
    widget1.setStyleSheet("background-color:#FFFFFF")
    window.show()
    app.exec_()

When you move your mouse into the first 100,100 pixel square, you will see the letter 'a' being printed in the terminal