Sorting a list of ints while ignoring sign [Python]

Question

I would like to sort a list of ints, where the desired behavior is

input:  [-2, 1, 4, -5]
output: [1, -2, 4, -5]

Treating it as a list of strings doesn't work, and neither does treating it as a list of ints as they return

string: [-2, -5, 1, 4]
ints:   [-5, -2, 1, 4]

Any pointers on how to received the desired behavior?

How would you like [-2, 1, 2, -2, 4, -5] to be sorted? [1, 2, -2, -2, 4, -5], [1, -2, -2, 2, 4, -5], or any arbitrary order for number with same abs value? — dfrib
– dfrib, Commented Feb 21, 2018 at 17:53

kindall · Accepted Answer · 2018-02-21 18:19:38Z

12

Use a key function that takes the absolute value to create the sort key for each item. Conveniently, Python has such a function built-in: abs().

original = [-2, 1, 4, -5]
original.sort(key=abs)

answered Feb 21, 2018 at 17:45

kindall

185k36 gold badges291 silver badges321 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

My only comment is not to overwrite the reserved name input.

You're right. I did that to match the question, but I changed it.

Joris Schellekens · Accepted Answer · 2018-02-21 17:51:08Z

1

I would suggest you define a function that calculates the absolute value (or the second power) of the number, and simply use that as the sort key.

answered Feb 21, 2018 at 17:51

Joris Schellekens

9,2173 gold badges28 silver badges60 bronze badges