[davidwf]

I am not a language expert, but Clojure (inspired by CLOS IIRC) does method resolution based on an arbitrary function that can ask any "is it a duck?" question of the arguments:

https://clojure.org/about/runtime_polymorphism

It's common for code to "choose" which method to call based on the class of the arguments, but it's also common to choose which method based on whether a particular key is in the hashmap, etc.

[mumblemumble]

I suppose that this is edging dangerously close to starting a semantic argument, but I'd personally argue that ad-hoc polymorphism is a distinct concept from duck typing that just happens to have a lot of overlap in its use cases. One key distinction is that Clojure multimethods need to be explicitly declared somewhere, whereas duck typing is 100% implicit.

[fulafel]

And in everyday Clojure usage the equivalent of Python attribute access is key access on maps, which is even more directly duck typed.