单例的实现方式:1、基于类#encoding=utf-8class Singleton(object): def __init__(self): pass @classmethod def instance(cls, *args, **kwargs): if not hasattr(Singleton, "_instance"): Singleton._instance = Singleton(*args, **kwargs) return Singleton._instances1 = Singleton.instance()s2 = Singleton.instance()print(s1 is s2)支持多线程:#encoding=utf-8import threadingclass Singleton(object): _instance_lock = threading.Lock() def __init__(self): pass @classmethod def instance(cls, *args, **kwargs): if not hasattr(Singleton, "_instance"):# with Singleton._instance_lock:#枷锁 if not hasattr(Singleton, "_instance"): Singleton._instance = Singleton(*args, **kwargs) return Singleton._instancedef task(arg): obj = Singleton.instance() print(obj)for i in range(10): t = threading.Thread(target=task,args=(i,)) t.start()obj = Singleton.instance()print(obj)2、利用__new__()#encoding=utf-8class Singleton(object): def __init__(self): pass def __new__(cls,*args,**kwargs): if not hasattr(cls,"_instance"): cls._instance = object.__new__(cls) return cls._instancep1 = Singleton()p2 = Singleton()print(p1 is p2)支持多线程方式#encoding=utf-8import threadingclass Singleton(object): _instance_lock = threading.Lock() def __init__(self): pass def __new__(cls,*args,**kwargs): if not hasattr(cls,"_instance"): with cls._instance_lock: if not hasattr(cls,"_instance"): cls._instance = object.__new__(cls) return cls._instancedef task(): obj = Singleton() print(obj)for i in range(20): t = threading.Thread(target=task,args=()) t.start()3、利用装饰器#encoding=utf-8import threadingdef Singleton(cls): _instance = {} def _singleton(*args,**kwargs): if cls not in _instance: _instance[cls] = cls(*args,**kwargs) return _instance[cls] return _singleton@Singletonclass Person(object):#Person = Singleton(Person) a = 10 def __init__(self,x=0): self.x = xp = Person(2)#_singleton(2)p2 = Person(3)print(p is p2)print(p.x)print(p2.x)示例1：#encoding=utf-8class Person(object): __instance = None#定义一个类变量，用于绑定实例对象 def __init__(self,name,age): self.name = name self.age = age @classmethod def get_instance(cls,name,age): if cls.__instance == None: cls.__instance =Person(name,age) return cls.__instance def get_info(self): return self.name + ":" + str(self.age)p1 = Person.get_instance("xxx",20)p2 = Person.get_instance("yyy",50)print(p1 is p2)print(p1.get_info())print(p2.get_info())#此种实现方式无法在生成实例后改变实例变量的值示例2：#encoding=utf-8class Singleton(object): _instance = None def __new__(cls,a,b,*args,**kwargs): if cls._instance == None: cls._instance = super(Singleton,cls).__new__(cls,*args,**kwargs) return cls._instanceclass Person(Singleton): def __init__(self,name,age): self.name = name self.age = age def getInfo(self): return "姓名: %s,年龄: %s" %(self.name,self.age)p1 = Person("张三",20)print(p1.getInfo())p2 = Person("李四",20)print(p1.getInfo())print(p1 is p2)print("类变量: ",Person._instance)示例3：#encoding=utf-8class Person(object): __instance = None#创建一个类变量用户存储类的实例对象 def __init__(self,name,age): self.name = name self.age = age def __new__(cls,name,age):#自定义Person自己的__new__()方法用于产生实例对象，此处需要传入name，age两个参数 if cls.__instance == None:#保证实例对象__instance只会被赋值一次，如果之前已经创建过实例，直接返回之前创建的实例 #cls.__instance = super(Person,cls).__new__(cls) cls.__instance = object.__new__(cls)#调用父类的__new__方法创建对象 return cls.__instance#返回实例对象 def getInfo(self): return "姓名: %s,年龄: %s" %(self.name,self.age)p1 = Person("h",20)print(p1.getInfo())p2 = Person("kkk",30)print(p1.getInfo())print(p2.getInfo())print(p1 is p2)'''以上代码执行过程：p1 = Person("h",20)首先调用__new__方法产生实例p1，此时Person的__instance为none所以会创建一个对象，然后调用__init__方法，把返回的实例对象__instance传入self中，并初始实例变量name，ageprint(p2.getInfo())首先调用__new__方法产生实例p2，此时Person的__instance为不为None,为p1,所以会直接返回对象p1，然后调用__init__方法，把返回的实例对象__instance传入self中，并用新的name，age初始实例变量name，age ''' 如果__init__有其他参数，__new__需要传入参数