Python - Fast Way to Remove Duplicates in This List?

Question

You know, to turn list:

a = ["hello", "hello", "hi", "hi", "hey"]

into list:

b = ["hello", "hi", "hey"]

You simply do it like this:

b = list(set(a))

It's fast and pythonic.

But what if i need to turn this list:

a = [["hello", "hi"], ["hello", "hi"], ["how", "what"], ["hello", "hi"], 
     ["how", "what"]] 

to:

b = [["hello", "hi"], ["how", "what"]]

What's the pythonic way to do it?

Answer 1

>>> a = [["hello", "hi"], ["hello", "hi"], ["how", "what"], ["hello", "hi"], ["how", "what"]]
>>> set(map(tuple, a))
set([('how', 'what'), ('hello', 'hi')])