The idea of stateless functional programming requires some care when using Python objects. Objects are typically stateful. Indeed, one can argue that the entire purpose of object-oriented programming is to encapsulate state change into class definitions. Because of this, we find ourselves pulled in opposing directions between functional programming and imperative programming when using Python class definitions to process collections.
The benefit of using a callable object to create a composite function gives us slightly simpler syntax when the resulting composite function is used. When we start working with iterable mappings or reductions, we have to be aware of how and why we introduce stateful objects.
