You're exactly describing duck typing. Resolving it at compile time in a static, "safe" way is a useful feature to be sure, but that doesn't mean it's not duck

You're exactly describing duck typing. Resolving it at compile time in a static, "safe" way is a useful feature to be sure, but that doesn't mean it's not duck typing. Replace "Go" with "Python" in your final paragraph and it's just as true. Implement __setitem__(key, value) and you can use it in a dict-like way such that you can say "foo[bar] = baz" where foo is an object of your defined type. Define __iter__ on your type and you can now say "for x in foo: ..."