import sys

# If using PyQt4, a QTreeWidget window with a single item will be created and
# the following will be printed on the console:
#    item in dummyList? True
#    dummyList.index(item) =  2
#from PyQt4 import QtGui


# If using PySide, no window will be shown, and the following trace will
# be printed on the console:
#    Traceback (most recent call last):
#      File "..... NotImplementedError_when_testing_for_membership_in_QTreeWidgetItem.py", line 29, in <module>
#        print('item in dummyList?', item in dummyList)
#    NotImplementedError: operator not implemented.
from PySide import QtGui


app = QtGui.QApplication(sys.argv)

treeWidget = QtGui.QTreeWidget()

item = QtGui.QTreeWidgetItem(['text of column 0'])
treeWidget.insertTopLevelItem(0, item)

dummyList = ['foo', 'bar', item]

# "item in dummyList" raises a NotImplementedError: operator not implemented.
print('item in dummyList?', item in dummyList)

# "dummyList.index(item)" raises a NotImplementedError: operator not implemented too.
print('dummyList.index(item) = ', dummyList.index(item))

treeWidget.show()

app.exec_()
sys.exit()