List to set

set(list)

Set to list

list(set)

Add

set.add('new_item')

Update

set.update([list])

Remove / Discard

set.remove('item') # will raise an error if item not found
# set.discard # will not raise error

Clear

set.clear()

Delete

del set

Union

set1.union(set2)
# set1.update(set2)

Difference

set(sentence1.lower()).difference(set(sentence2.lower()))
# set(sentence1.lower()) - set(sentence2.lower())