class Foo(object):
    instance = None

    def __init__(self):
        pass
    def process(self):
        return ‘1234565‘

    @classmethod   #版本1單例模式
    def get_instance(cls):
        if  Foo.instance:
            return Foo.instance
        else:
            Foo.instance = Foo()
            return
 
 Foo.instance


obj1 = Foo()
print(obj1.process())

obj2 = Foo()
print(obj2.process())
obj1不相等obj2  id(obj1)

obj1 = Foo.get_instance()
obj2 = Foo.get_instance()
此時的obj1=obj2


class Foo(object):
    instance = None

    def __init__(self):
        self.name = ‘alex‘

    def __new__(cls, *args, **kwargs):
        
 
if Foo.instance:
            return Foo.instance
        else:
            obj = object.__new__(cls, *args, **kwargs) #創建對象的本質是new  new先執行
            return return obj

obj1 = Foo()
obj2 = Foo()
print(id(obj1), id(obj2))  obj1=obj2  單例模式2 高級版  永遠用一個對象的實例！

創建的對象內部封裝的值是一樣的 就搞成單例模式

python中對單例模式的理解