New-Style classes in Python

Actually not really new (introduced in 2.2)

Concept

Descriptors (descriptor protocol)::

• Properties, bound/unbound method call, static / class method are all based on the 'descriptor protocol'

Descriptor

Definition:

• object attribute with 'binding behavior'

Classification:

Example:

  print boy.name

Flow:

The simplest case is
  boy.__dict__['name']
  type(boy).__dict__['name']
  type(boy).__base__.__dict__['name']

If, a valid entry is looked up in the dictionary.
  and if the entry is a object with '__get__', '__set__', '__delete__'
  then it is a 'data-desc'
  the descriptor protocol will be used.

Each 'Object' have "attributes"

• data properties
• methods

Notes for 'overriding MAGIC method'

• descriptor is always triggered by getattribute()

  • so, if you override getattribute, you need to to implement the descriptor protocol handling, otherwise, descriptor won't work anymore

Ref: How-To Guide for Descriptor:

• http://users.rcn.com/python/download/Descriptor.htm