[Tutor] sorted question

[It't me]

Hi all,

I'm learning Python with Google's Python class

Ik have a question about the following code:
=================================
def sort(var):
 return var[-1]  #returns the last character of var

def sort_last():
  tup = [(1, 3), (3, 2), (2, 1)]
  print(sorted(tup, key=sort))

sort_last()
==================================

I uderstand everything except (var) value.
I understand that key=sort calls the sort function.
But where comes the var value from?
Does sort automatic pass the value from tup to (var)

because (var) is nowhere defined.

Thanks,

Martin
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