单例模式中的四种方式

#先写一个setting模块用来存放（ip=None，port=None）
import setting
class Mysql:
    __instance=None
    def __init__(self,ip,port):
        self.ip=ip
        self.port=port
    @classmethod
    def srea(cls):
        if cls.__instance is None:
            cls.__instance=cls(setting.ip,setting.port)
        return cls.__instance
obj=Mysql.srea()
obj1=Mysql(‘1.1.1.1‘,203)
print(obj)
print(obj1)

import setting
def atuh(cls):
    _instance=cls(setting.ip,setting.port)
    def warpper(*args,**kwargs):
        if args or kwargs:
            obi=cls(*args,**kwargs)
            return obi
        return _instance
    return warpper
@atuh
class Mysql:
    def __init__(self,ip,port):
        self.ip=ip
        self.port=port
obj=Mysql()
obj1=Mysql()
obj2=Mysql(‘1.1.1.1‘,2206)
print(obj)
print(obj1)
print(obj2)

import setting
class Mymeta(type):
    def __init__(self,mysql,mysql_obj,mysql_dic):
        self._instance=self(setting.ip,setting.port)
    def __call__(self, *args, **kwargs):
        if args or kwargs:
            obj=self.__new__(self)
            self.__init__(obj,*args,**kwargs)
            return obj
        else:
            return self._instance
class Mysql(metaclass=Mymeta):
    def __init__(self,ip,port):
        self.ip=ip
        self.port=port
obj=Mysql()
obj1=Mysql()
obj2=Mysql(‘1.1.1.3‘,2206)
print(obj)
print(obj1)
print(obj2)

song模块的代码如下：class Mysql:
    def __init__(self,ip,port):
        self.ip=ip
        self.port=port
instance=Mysql(‘1.1.1.1‘,2206)
主题代码吐下：
def f():
    from song import instance
    print(instance)
def f2():
    from song import instance, Mysql
    odj=Mysql(‘1.1.1.1‘,2206)
    print(odj)
f()
f2()