class - What is the difference between old style and new style classes in Python? -



class - What is the difference between old style and new style classes in Python? -

what difference between old style , new style classes in python? there ever reason utilize old-style classes these days?

from http://docs.python.org/2/reference/datamodel.html#new-style-and-classic-classes :

up python 2.1, old-style classes flavour available user. concept of (old-style) class unrelated concept of type: if x instance of old-style class, x.__class__ designates class of x, type(x) <type 'instance'>. reflects fact old-style instances, independently of class, implemented single built-in type, called instance.

new-style classes introduced in python 2.2 unify concepts of class , type. new-style class user-defined type, no more, no less. if x instance of new-style class, type(x) typically same x.__class__ (although not guaranteed – new-style class instance permitted override value returned x.__class__).

the major motivation introducing new-style classes provide unified object model total meta-model. has number of immediate benefits, ability subclass built-in types, or introduction of "descriptors", enable computed properties.

for compatibility reasons, classes still old-style default. new-style classes created specifying new-style class (i.e. type) parent class, or "top-level type" object if no other parent needed. behaviour of new-style classes differs of old-style classes in number of of import details in add-on type returns. of these changes fundamental new object model, way special methods invoked. others "fixes" not implemented before compatibility concerns, method resolution order in case of multiple inheritance.

python 3 has new-style classes. no matter if subclass object or not, classes new-style in python 3. recommended still subclass object.

python class oop types new-style-class

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