Without using additional libraries:
listOfItems = [['A','A','A'],['A','B','C'],['A','A','A'],['A','B','B'],['A','B','C']]
setOfItems = []
newListOfItems = []
for item in listOfItems:
if item in setOfItems:
continue
setOfItems.append(item)
temp = list(item)
occurence = listOfItems.count(item)
temp.append(occurence)
newListOfItems.append(temp)
print newListOfItems
Result is:
>>> print newListOfItems
[['A', 'A', 'A', 2], ['A', 'B', 'C', 2], ['A', 'B', 'B', 1]]