Can I do animal.bark() or animal.fly() ? All I know is that it's an Animal of some sort, may or may not be an instance of the Dog or Bird subclasses of Animal.
This kind of synthetic example is silly, though. The fundamental questions would be the same in Python as well. How did you end up with this heterogeneous collection of objects? Why are you unable to get a collection of objects that are known to support your desired protocol at that point? What happens if they don't? Etc, etc, etc. You might make very different design choices in a statically or dynamically typed language but thinking about zoos and animals with no context isn't particularly informative.
Synthetic? Yes. Contrived? No. I've seen this sort of thing in my own and other people's Java code, where you know what class it is but not the most-derived subclass. That's how polymorphism happens.
Right. It doesn't happen by rooting around objects looking for methods by name. That's usually a sign of some misdesign that's making you re-invent the polymorphic mechanisms of the language yourself. True both in Java and Python.
I agree that polymorphism is the "right way" if there's already a class hierarchy established.
If the superclass-subclass relationships aren't in place for you (worse yet, they're not set up how you want them to be set up), this hack accomplishes a similar effect with no refactoring.