python元类示例

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#Author:Runcheng
class_name = "Spam"
base = ()
def run(self):
    print("%s is runing" % self.name)

class_dict = {
    "name":"zou",
    "run":run
}
S = type("Spam", base, class_dict)
print(S)
print(type(S))
s = S()
print(type(s))
s.run()


# 利用type产生元类
SB = type("SB", (object,), {})
s = SB()
s.name = "zou"
print(type(s))     # <class '__main_ _.SB'>
print(s.__dict__)  # {'name': 'zou'}


# 3 自定义元类限制注释信息
from collections import Iterable,Iterator
class Mymeta(type):
    def __init__(self, class_name, base=None, dict=None ):
        print(self)
        print(class_name)
        print(base)
        print(dict)
        for key in dict:
            if not callable(dict[key]):continue
            if not dict[key].__doc__:
                raise Exception("你还没写注释信息")

    def __call__(self, *args, **kwargs):
        print("from mytype",self,args,kwargs) # from mytype <class '__main__.Foo'> ('zou',) {}
        obj = self.__new__(self)
        self.__init__(obj, *args, **kwargs)
        return obj


class Foo(metaclass=Mymeta):
    x = 1
    def __init__(self,name):
        "注释信息" # 不写这里的注释，直接抛出元类的异常信息
        self.name = name
    def run(self):
        "run function"
        print("running")


f = Foo("zou")      # from mytype <class '__main__.Foo'> ('zou',) {}
print(Foo.__dict__)