Question

In Python lists, there are two alternative ways of performing a list sort:

1. Using its .sort method, which sorts in place
2. Using the sorted() built-in function, which returns a new sorted list

Now, if I create a custom container type (say by subclassing from itertools‘s ABC), can I do the same?

I can figure out how to make the custom container object sorts in place. But what I want is for the built-in sort() to return a new instance of that custom container object (instead of a list) when I use it.

Is this possible? If so, how?

Answer 1

What about just subclassing the builtin list, and just redefining sort method ?

>>> class MyList(list):
    def sort(self):
        copy = list(self)
        copy.sort()
        return MyList(copy)


>>> l2 = MyList([2, 6, 9, 8])
>>> l2
[2, 6, 9, 8]
>>> l3 = l2.sort()
>>> l2
[2, 6, 9, 8]
>>> l3
[2, 6, 8, 9]
>>> 

EDIT: after the OP’s comment, leaving sort method as is and adding a new one:

>>> class MyList(list):
    def sort_copy(self):
        copy = list(self)
        copy.sort()
        return MyList(copy)

The sort method inherited from parent remains as is (in place), the new sort_copy method creates a new one.