python factory method relative to the instance itself, (class method also using self as argument?)

Question

So I have this piece of code originally,

class Foo:
    def __init__(self, val:int):
        self.val = val

    def next(self) -> Foo:
        """
        Returns:
            Foo: Foo with value 1 bigger than the current
        """
        return Foo(self.val+1)

which, the next() method is to generate another Foo instance based on the current instance.

It works fine so far, but then I have read about static method and class method in python, and it seemed that I might should using a class method for next(), as it is a factory method (please point out if I got the idea wrong!)

What would be the most elegant way to implement the above?

Answer 1

Consider:

class Foo:
    index = 0
    def __init__(self):
        self.val = Foo.index
        Foo.index += 1

Now, you just have to do:

zero = Foo()
one = Foo()

And if you want to force a starting value:

Foo.index = 99
n99 = Foo()
n100 = Foo()