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    <p>Just to add a specific example of a good use from my answer <a href="https://stackoverflow.com/questions/3834263/is-clojures-multi-method-dispatch-truly-superior-say-to-what-i-can-do-in-pytho/3842928#3842928">here</a>, coupled with decorators a simple mechanism for multimethods can be done.</p> <pre><code># This is in the 'mm' module registry = {} import inspect class MultiMethod(object): def __init__(self, name): self.name = name self.typemap = {} def __call__(self, *args): types = tuple(arg.__class__ for arg in args) # a generator expression! function = self.typemap.get(types) if function is None: raise TypeError("no match") return function(*args) def register(self, types, function): if types in self.typemap: raise TypeError("duplicate registration") self.typemap[types] = function def multimethod(function): name = function.__name__ mm = registry.get(name) if mm is None: mm = registry[name] = MultiMethod(name) spec = inspect.getfullargspec(function) types = tuple(spec.annotations[x] for x in spec.args) mm.register(types, function) return mm </code></pre> <p>and an example of use:</p> <pre><code>from mm import multimethod @multimethod def foo(a: int): return "an int" @multimethod def foo(a: int, b: str): return "an int and a string" if __name__ == '__main__': print("foo(1,'a') = {}".format(foo(1,'a'))) print("foo(7) = {}".format(foo(7))) </code></pre> <p>This can be done by adding the types to the decorator as <a href="http://www.artima.com/weblogs/viewpost.jsp?thread=101605" rel="nofollow noreferrer">Guido's original post</a> shows, but annotating the parameters themselves is better as it avoids the possibility of wrong matching of parameters and types.</p> <p><em>Note</em>: In Python you can access the annotations as <code>function.__annotations__</code> rather than <code>function.func_annotations</code> as the <code>func_*</code> style was removed on Python 3.</p>
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    1. POWhat are good uses for Python3's "Function Annotations"
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    1. USMuhammad Alkarouri
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    1. COInteresting application, though I'm afraid `function = self.typemap.get(types)` won't work when subclasses are involved. In that case you'd probably have to loop through `typemap` using `isinnstance`. I wonder if [`@overload`](https://pypi.python.org/pypi/overload) handles this correctly
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      1. USTobias Kienzler
 

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