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'

You can't use a two parameter lambda as the key for sort. It passes in each item one at a time. — Morgan Thrapp
– Morgan Thrapp, Commented Oct 12, 2016 at 14:46
You are confusing the cmp and key arguments; cmp is entirely gone from Python 3. For key, just use key=lambda x: x.finish — Martijn Pieters
– Martijn Pieters, Commented Oct 12, 2016 at 14:47
it is a list of time interval... def__init__(self, title, start, finish): — steph
– steph, Commented Oct 12, 2016 at 15:15

alecxe · Accepted Answer · 2016-10-12 14:47:43Z

2

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"))

answered Oct 12, 2016 at 14:47

alecxe

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1 Comment

thanks for the quick... What I want to do, is to sort by the interval of two finish