self.actionZoomIn = QtGui.QAction('Zoom In', self)
self.actionZoomOut = QtGui.QAction('Zoom Out', self)
key = QtCore.Qt.CTRL | QtCore.Qt.Key_Equal
self.actionZoomIn.setShortcut(QtGui.QKeySequence(key))

self.actionZoomOut.setShortcut(QtGui.QKeySequence('Ctrl+-'))