单例的5种开启方式
单例模式:多次实例化结果指向同一个实例
第一种(基于classmethod)
class Mysql(object): _instance = None def __init__(self, ip, port): self.ip = ip self.port = port @classmethod def singleton(cls): if not cls._instance: cls._instance = Mysql('127.0.0.1', 3306) return cls._instance obj1 = Mysql.singleton() obj2 = Mysql.singleton() print(obj1) print(obj2)
第二种(基于装饰器)
def singleton(cls): # 该对象在类Mysql被装饰上singleton的时候就已经实例化完毕 _instance = cls('127.0.0.1',3306) def inner(*args,**kwargs): # 判断是否传入参数，传入参数表示要实例化新的，不传表示用默认的 if args or kwargs: obj = cls(*args,**kwargs) return obj return _instance return inner @singleton class Mysql: def __init__(self,ip,port): self.ip = ip self.port = port obj1 = Mysql() obj2 = Mysql() obj3 = Mysql() print(obj1,obj2,obj3)
第三种(基于元类)
class MymetaClass(type): def __call__(self, *args, **kwargs): if not hasattr(self,'instance'): self.instance = super().__call__(*args,**kwargs) return self.instance class Mysql(metaclass=MymetaClass): def __init__(self,host,port): self.host = host self.port = port obj = Mysql('ajdak',213) obj1 = Mysql('asdasdas',134234) print(obj,obj1)
第四种(基于__new__)
class Singleton(object): _instance = None def __new__(cls, *args, **kw): if not cls._instance: cls._instance = super(Singleton, cls).__new__(cls, *args, **kw) return cls._instance class MyClass(Singleton): a = 1
第五种(基于模块)
# 单独在一个py文件中定义一个类，并实例化一个对象，之后在其他文件导入这一对象，实现单例
class Singleton(object): def __init__(self,host,port): self.host = host self.port = port singleton = Singleton('127.0.0.1',3306)
单例模式是一种设计模式，实现单例模式的方式方法有很多，所以本文列出的只是其中的几种而已，不喜勿喷！
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第一种(基于classmethod)
class Mysql(object): _instance = None def __init__(self, ip, port): self.ip = ip self.port = port @classmethod def singleton(cls): if not cls._instance: cls._instance = Mysql('127.0.0.1', 3306) return cls._instance obj1 = Mysql.singleton() obj2 = Mysql.singleton() print(obj1) print(obj2)
第二种(基于装饰器)
def singleton(cls): # 该对象在类Mysql被装饰上singleton的时候就已经实例化完毕 _instance = cls('127.0.0.1',3306) def inner(*args,**kwargs): # 判断是否传入参数，传入参数表示要实例化新的，不传表示用默认的 if args or kwargs: obj = cls(*args,**kwargs) return obj return _instance return inner @singleton class Mysql: def __init__(self,ip,port): self.ip = ip self.port = port obj1 = Mysql() obj2 = Mysql() obj3 = Mysql() print(obj1,obj2,obj3)
第三种(基于元类)
class MymetaClass(type): def __call__(self, *args, **kwargs): if not hasattr(self,'instance'): self.instance = super().__call__(*args,**kwargs) return self.instance class Mysql(metaclass=MymetaClass): def __init__(self,host,port): self.host = host self.port = port obj = Mysql('ajdak',213) obj1 = Mysql('asdasdas',134234) print(obj,obj1)
第四种(基于__new__)
class Singleton(object): _instance = None def __new__(cls, *args, **kw): if not cls._instance: cls._instance = super(Singleton, cls).__new__(cls, *args, **kw) return cls._instance class MyClass(Singleton): a = 1
第五种(基于模块)
# 单独在一个py文件中定义一个类，并实例化一个对象，之后在其他文件导入这一对象，实现单例
class Singleton(object): def __init__(self,host,port): self.host = host self.port = port singleton = Singleton('127.0.0.1',3306)
单例模式是一种设计模式，实现单例模式的方式方法有很多，所以本文列出的只是其中的几种而已，不喜勿喷！
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