How does a Python custom comparator work?

Question

I have the following Python dict:

[(2, [3, 4, 5]), (3, [1, 0, 0, 0, 1]), (4, [-1]), (10, [1, 2, 3])]

Now I want to sort them on the basis o

Answer 1

First, the cmp() function:

cmp(...)
    cmp(x, y) -> integer
    Return negative if xy.

You are using this line: items.sort(myComparator) which is equivalent to saying: items.sort(-1) or items.sort(0) or items.sort(1)

Since you want to sort based on the sum of each tuples list, you could do this:

mylist = [(2, [3, 4, 5]), (3, [1, 0, 0, 0, 1]), (4, [-1]), (10, [1, 2, 3])]
sorted(mylist, key=lambda pair: sum(pair[1]))

What this is doing is, I think, exactly what you wanted. Sorting mylist based on the sum() of each tuples list