class RoundWindow(QtWebKit.QWebView):

    def __init__(self):
        super(RoundWindow, self).__init__()
self.initUI()

def initUI(self):
    self.setWindowFlags(Qt.FramelessWindowHint)
self.setAttribute(Qt.WA_TranslucentBackground)

def sizeHint(self):
    return QSize(300, 300)

def paintEvent(self, event):
    qp = QtGui.QPainter()
qp.begin(self)
qp.setRenderHint(QtGui.QPainter.Antialiasing)
qp.setPen(Qt.NoPen)
qp.setBrush(QtGui.QColor(255, 0, 0, 127))
qp.drawEllipse(0, 0, 300, 300)
qp.end()
a = QtGui.QApplication([])
rw = RoundWindow()
rw.show()
a.exec_()
PyQt Irregularly Shaped Windows (e.g. A circular without a border/decorations)