import sys
from PyQt4 import QtCore, QtGui

class Window(QtGui.QWidget):
def __init__(self):
super(Window, self).__init__()
self.scroll = QtGui.QScrollArea()
self.widget = QtGui.QGraphicsView()
self.widget.setFixedSize(600, 600)
self.scroll.setWidget(self.widget)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.scroll)
self.scroll.viewport().installEventFilter(self)

def eventFilter(self, source, event):
if (event.type() == QtCore.QEvent.Wheel and
source is self.scroll.viewport()):
return True
return super(Window, self).eventFilter(source, event)

if __name__ == '__main__':

app = QtGui.QApplication(sys.argv)
window = Window()
window.setGeometry(600, 100, 400, 300)
window.show()
sys.exit(app.exec_())