On Fri, May 13, 2016 at 1:10 AM Ben Finney <ben+pyt...@benfinney.id.au> wrote:
> Howdy all, > > Ever since Python's much-celebrated Grand Unification of classes and > types, I have used those terms interchangeably: every class is a type, > and every type is a class. > > That may be an unwise conflation. With the recent rise of optional type > annotation in Python 3, more people are speaking about the important > distinction between a class and a type. > The concept of a type existed before the concept of object-oriented programming. A type is more of a mathematical concept. Do some reading on "type theory" if you'd like to know more. A type system ideally allows logical deductions about the validity of your expressions/statements. Stuff a static analyzer is good at. With the advent of object-orientation and the concept of inheritance, things have gotten a little confused. You could make a distinction between "type inheritance" and "implementation/code inheritance" but many languages do not. When you make a subclass in Python, it inherits both the type and the code of the superclass. I suppose you could say the composition vs inheritance argument stems from some people advocating code inheritance without type inheritance. -- https://mail.python.org/mailman/listinfo/python-list
