In Python, since functions can be defined anywhere, and decorators can execute arbitrary code (including registering and running the functions they decorate) and be passed variables from the scope they're used, you can make some pretty powerful DSLs. And method_missing delegation can largely be replaced by defining classes at runtime, especially now that people are getting used to passing hashes as arguments (in fact, Rails seems to be slowly deprecating find_by_foo_and_bar in favor of where(foo: _, bar: _)?).