Same name functions in same class – is there an elegant way to determine which to call?

Inheritance is probably the best way to do this, but since you asked specifically about decorators, I wanted to show you could do this using decorators.

You’ll need to use a dictionary to store your functions by version, and then look up which version to use at runtime. Here’s an example.

version_store = {}

def version(v):
    def dec(f):
        name = f.__qualname__
        version_store[(name, v)] = f
        def method(self, *args, **kwargs):
            f = version_store[(name, self.version)]
            return f(self, *args, **kwargs)
        return method
    return dec

class Product(object):
    def __init__(self, version):
        self.version = version

    @version("1.0")
    def function(self):
        print("1.0")

    @version("2.0")
    def function(self):
        print("2.0")

Product("1.0").function()
Product("2.0").function()