Ostensibly, Python has a more Java-like model of method invocation, but this is really only a semantic difference. There is little that you can do with Python

Ostensibly, Python has a more Java-like model of method invocation, but this is really only a semantic difference. There is little that you can do with Python methods that you can't do with Ruby's methods and vice-versa. Generally, checking the type with isinstance is considered bad practice although it can be useful sometimes (I can't think of any simple examples off the top of my head though). The main reason I can think of for using an interface or abc is simply so that if you forget to add a required method, the exception gets thrown sooner rather than later. Plus with an abc, you also allow the base class to define methods that depend upon abstract methods (for instance, if you subclass the Mapping abc, you get __contains__, keys, items, etc for adding __getitem__). Strictly speaking, there's no reason why you can't do that without an abstract base class, but it makes it easier. In short, there are useful reasons to have interfaces and abstract base classes in Python, but they probably aren't the same reasons you'd want them in a statically-typed language like Java.