test_metaclass

test_metaclass.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# @file     test_metaclass.py
# @author   kaka_ace <xiang.ace@gmail.com>
# @date     Nov 03 2015
# @brief     
#


class MyMeta(type):
    def __new__(cls, name, bases, d):
        print("-------------- meta new --------------")
        print(cls)
        print(name)
        print(bases)
        print(d)
        cls = type.__new__(cls, name, bases, d)
        return cls

    def __init__(cls, name, bases, d):
        print("-------------- meta init --------------")
        print(cls)
        print(name)
        print(bases)
        print(d)
        super(MyMeta, cls).__init__(name, bases, d)

    def __call__(cls, *args, **kwargs):
        print("-------------- meta call --------------")
        print(cls)
        print(args)
        print(kwargs)
        return type.__call__(cls, *args, **kwargs)


class Base(metaclass=MyMeta):
    STATUS = 1

    def __new__(cls, *args, **kwargs):
        print("-------------- Base new --------------")
        print(cls)
        print(args)
        print(kwargs)
        return super(Base, cls).__new__(cls)  # object 不需要加参数啦

    def __init__(self, *args, **kwargs):
        print("-------------- Base init --------------")
        print(self)
        print(args)
        print(kwargs)
        super(Base, self).__init__()

# 此时输出:
# meta new Base
# meta init Base


class Derive(Base):
    D_STATUS = 1

    def __new__(cls, *args, **kwargs):
        print("-------------- Derive new --------------")
        print(cls)
        print(args)
        print(kwargs)
        return super(Derive, cls).__new__(cls, *args, **kwargs)

    def __init__(self, *args, **kwargs):
        print("-------------- Derive init --------------")
        print(self)
        print(args)
        print(kwargs)
        super(Derive, self).__init__(*args, **kwargs)

# 此时输出:
# meta new Derive
# meta init Derive

"""
b 实例生成过程:
meta call
Base new
b 实例生成
b init -> Base init
"""
b1 = Base(1)


"""
d 实例生成过程:
meta call
Derive new
Base new
b 实例生成
b init -> Derive init -> Base init
"""
d1 = Derive('a')

print("-----------------------------")
# 同 b1, d1
b2 = Base()
d2 = Derive()