I think typing_extensions.Protocol helps support the general duck typing "any object that has method x", though there are some implementation issues w/ dataclasses and such..
That won't help if I want to square a matrix, or a polynomial.
> typing_extensions.Protocol helps support the general duck typing "any object that has method x"
Even if there's a `powerable` protocol that could be used to annotate `square` and `cube`, how would you annotate a slightly more complex function like `poly`?
def square(x): return x**2
def cube(x): return x**3
def poly(x): return 3 * x**2 + 2 * xWhat’s you want is something like “commutative multiplication”
From comments? They are again limited by the authors imagination. From reading the source?
In quite a few cases where one would overload a mathematical operation to, say, sum two objects of certain type, it'd be better to explicitly type out the operation as a functor/lambda.
How would you use type annotations to show that `square` accepts a matrix (as well as an int, float, rational number etc.)?
Semi-seriously: by specifying the input type is a Monoid.
How do you find out that a function exists, what it accepts, and what it does normally?
> From comments? They are again limited by the authors imagination.
Sure, but an author which much experience with duck typing will typically write documentation that specified that expected methods (informal structural “types”) rather than nominal types.
With the static equivalent (protocols), it’s conceivable that this is also discoverable via tooling.