Python - Why is arr.sort() None?

Question

arr = [34, 67, 34]
print(arr.sort())
print(sorted(arr))

Answer 1

arr.sort() modifies the list in place and doesn't return anything (when this happens Python adds a "return None"). It's supposed to be used alone:

arr.sort() # No print

https://www.quora.com/What-is-the-difference-between-sort-and-sorted-function-in-Python