Why is this code snippet not working?

Question

Python

This code should take a numeric int value and then sort it in descending order

def descending_order(num):
    output = [x for x in str(num)]
    return output.sort(reverse=True)

But for some reason the function doesn't return anything.

Answer 1

The sort method returns nothing. So it is necessary to separate sorting and return.
Or, you can use sorted instead of sort:

def descending_order(num):
  return sorted(str(num), reverse=True)

Answer 2

read the doc on sort