how to find what is uncommon between two sets python code example

Example: get list of words that are in two lists using set

list1 = ['little','blue','widget']
list2 = ['there','is','a','little','blue','cup','on','the','table']

list3 = set(list1)&set(list2) # we don't need to list3 to actually be a list

list4 = sorted(list3, key = lambda k : list1.index(k))