class_._instances[class_] = super(Singleton, class_).__call__(*args, **kwargs) returnclass_._instances[class_] classMyClass(BaseClass): __metaclass__= Singleton
class Singleton: _instance = None @classmethod def get_instance(cls): if not cls._instance: cls._instance = cls() return cls._instance def __init__(self): if Singleton._instance is not None: raise Exception("This class is a singleton!") # 初始化逻辑.....
二、baseclass classSingleton(object): _instance=Nonedef__new__(class_, *args, **kwargs):ifnotisinstance(class_._instance, class_):#class_._instance = object.__new__(class_) 这行语句和下一行语句作用一样的class_._instance=super(Singleton,class_).__new__(class_)returnclass_._instancec...
步骤二:创建子类 接下来,我们创建一个子类,继承基类SingletonBase,并在子类中实现单例模式的具体逻辑。 classSingleton(SingletonBase):def__init__(self):ifself._instance:raiseException("This class is a singleton!")self._data=[]defadd_data(self,item):self._data.append(item)defget_data(self):retur...
class BaseController(object): _singleton = None def __new__(cls, *a, **k): if not cls._singleton: cls._singleton = object.__new__(cls, *a, **k) return cls._singleton 这段代码出自 https://github.com/bottlepy/bottle/blob/release-0.6/bottle.py 这就是通过 __new__ 方法是实现单...
class SingletonMeta(type): """ The Singleton class can be implemented in different ways in Python. Some possible methods include: base class, decorator, metaclass. We will use themetaclassbecause it is best suited for this purpose. """ _instances = {} def __call__(cls, *args, **kwarg...
single=Singleton()# 创建第二个实例 double=Singleton()# Error Output:# Exception:Singletonclasscanonly have one instance. 在这里,当尝试实例化double时,代码会失败,因为它通过检查类属性_instance的状态,检测到Singleton的实例已经存在。我们可以通过检查该属性来明确了解这一情况: ...
class SingletonBase(type): def __init__(self,*args,**kwargs): self._instance=None super().__init__(*args,**kwargs) def __call__(self,*args,**kwargs): if self._instance is None: self._instance=super(SingletonBase,self).__call__(*args,**kwargs) ...
1#使用__metaclass__(元类)的高级python用法2classSingleton2(type):3def__init__(cls,name,bases,dict):4super(Singleton2,cls).__init__(name,bases,dict)5cls._instance=None6def__call__(cls,*args,**kw):7ifcls._instance is None:8cls._instance=super(Singleton2,cls).__call__(*args,*...
class Base:passclass Child:pass# 等价定义 注意 Base 后要加上逗号否则就不是 tuple 了SameChild = type('Child', (Base,), {})# 加上方法class ChildWithMethod(Base):bar = Truedef hello(self):print('hello')def hello(self):print('hello')# 等价定义ChildWithMethod = type('ChildWithMethod'...