Python error in sorting a list

Question

I simply want to sort a list... and I have a 2 parameter lambda Here is my simple code:

I.sort(key = lambda x, y: x.finish - y.finish)

And the compiler return this error

builtins.TypeError: <lambda>() missing 1 required positional argument: 'y'

Answer 1

You are trying to use key function as a cmp function (removed in Python 3.x), but don't you mean to simply sort by the "finish" attribute:

I.sort(key=lambda x: x.finish)

Or, with the "attrgetter" :

from operator import attrgetter

I.sort(key=attrgetter("finish"))