单例模式的实现

1. 重写__new__( ) 方法

# Author:ZJF
class Singletion(object):
    def __init__(self,name,age,job):
        self.name=name
        self.age=age
        self.job=job
        
    def __new__(cls, *args, **kwargs):
        if not hasattr(cls,'_instance'):
            orig = super(Singletion, cls)
            cls._instance = orig.__new__(cls,)
        return cls._instance

class MyClass(Singletion):
    a = 1

a = MyClass('小刚', '25', None)
print(a)
b = MyClass('小明', '26', "teacher")
print(b)
print(a)

2. 共享属性

class Borg(object):
    _state = {}
    def __init__(self,name,age,job):
        self.name=name
        self.age=age
        self.job=job
    def __new__(cls, *args, **kwargs):
        ob = super(Borg, cls).__new__(cls,)
        ob.__dict__=cls._state
        return ob

a = Borg('小刚', '25', None)
print(a.name)
b = Borg('小明', '26', "teacher")
print(b.name)
print(a.name)
a.name="李"
print(a.name,b.name)

3. 装饰器

def singleton(cls,*args,**kwargs):
    instances={}
    def getinstance(*args,**kwargs):
        if cls not in instances:
            instances[cls]=cls(*args,**kwargs)
        return instances[cls]
    return getinstance

@singleton
class Myclass(object):
    def __init__(self,name,age,job):
        self.name=name
        self.age=age
        self.job=job

a=Myclass('zt', '36', '保洁')
print(a.name,a)

b=Myclass('zsk', '99', None)
print(b.name,b)