Advanced Python 3 Programming Techniques

Chapter 9. Functors

In Python a function object is an object reference to any callable, such as a function, a lambda function, or a method. The definition also includes classes, since an object reference to a class is a callable that, when called, returns an object of the given class—for example, x = int(5). In computer science a functor is an object that can be called as though it were a function, so in Python terms a functor is just another kind of function object. Any class that has a __call__() special method is a functor. The key benefit that functors offer is that they can maintain some state information. For example, we could create a functor that always strips basic punctuation from the ends of a string. We would create and ...