from PySide import QtGui
from PySide import QtCore

class MyClass(QtGui.QStandardItem):
    def __init__(self):
        super(MyClass, self).__init__()

class SomeWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(SomeWidget, self).__init__(parent)
        self.setLayout(QtGui.QVBoxLayout())
        self.menu = QtGui.QMenu()
        self.layout().addWidget(self.menu)
        a = QtGui.QAction('sender test default object', self.menu)
        a.setData('test')
        a.triggered.connect(self.printSender) # this sends the default object (string) as data
        self.menu.addAction(a)

        a = QtGui.QAction('sender test custom object', self.menu)
        myClassInstance = MyClass()
        a.setData(myClassInstance)
        self.menu.addAction(a)
        a.triggered.connect(self.printSender) # this does not send the custom object as data in PySide 1.2.1 and later

    def printSender(self):
        sender = self.sender()
        print 'sender is:', sender
        print 'sender data is:', sender.data()

w = SomeWidget()
w.show()