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Comment by jakobnissen | Hacker News Reader

Python's single dispatch just means that if I do `foo.bar()`, the meaning of bar depends on the type of `foo`. So that is not recent, but a core part of the language.

Another difference to Python is that you can't add new methods post-hoc to types in Python. That's a big problem, but this has nothing to do with single/multiple dispatch. E.g. Rust has single dispatch but allows post-hoc methods.

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> you can't add new methods post-hoc to types in Python

Unless I'm misunderstanding what that means, you totally can:

    >>> class Foo:
    ...     def bar(self):
    ...         return 3
    ...
    >>> foo = Foo()
    >>> foo.bar()
    3
    >>> Foo.baz = lambda self: 6
    >>> foo.baz()
    6
    >>>

So just to clarify since it perhaps wasn't clear, I'm talking about singledispatch from the standard library: https://docs.python.org/3/library/functools.html#functools.s...

> Another difference to Python is that you can't add new methods post-hoc to types in Python.

Yes, you can. Heck, you can post-hoc add new methods to instances in python, too.

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