[Tutor] 'Last' in Python?

[Dave Friedman]

Hi all,

I'm teaching myself Python in part with Google's course, and one of the
exercises is to sort a list of tuples by the last element.
e.g.: a list [(1, 7), (1, 3), (3, 4, 5), (2, 2)] yields [(2, 2), (1, 3),
(3, 4, 5), (1, 7)].

My answer, after figuring out lambda functions, is
def sort_last(tuples):
  return sorted(tuples, key= lambda t: t[-1])

Google's answer is much more straightforward, except for one part.
def sort_last(tuples)
  return sorted(tuples, key=last)

What is 'last', and where can I find a description of it? Searching the web
and the python docs hasn't been helpful. (Maybe I'm searching badly?)
Insight and pointers appreciated.

Thanks,
-Dave
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