Searching through a list of tuples

[Repton]

I often find myself storing data in a list of tuples, and I want to ask
questions like "what is the index of the first tuple whose 3rd element
is x", or "give me the first tuple whose 2nd element is y".

I know I can do [elem for elem in lst if elem[3] == x][0] or (elem for
elem in lst if elem[2] == y).next() but it feels kinda ugly; is there a
better way?

(something like lst.index(x, key=..) or lst.find(y, key=..) would be
nice)

-- 
John.