Python3的__new__进行构造类的实例化
__new__方法
- 这个方法是用来生成类的实例
class Singleton(object):
def __new__(cls,*args, **kwargs): ①
if not hasattr(cls,'_inst'):
print(cls)
cls._inst = super(Singleton, cls).__new__(cls) ②
return cls._inst ②
① 第一个参数必须是"要进行实例化的类".
② 返回实例完成的结果,如果实例化失败那么实例的初始化函数"init"肯定不会执行
Python2(2.7)的写法
class Singleton(object):
def __new__(cls,*args, **kwargs): ①
if not hasattr(cls,'_inst'):
print(cls)
cls._inst = super(Singleton, cls).__new__(cls,*args,**kwargs) ②
return cls._inst ②
Python3(3.5)的写法
class Singleton(object):
def __new__(cls,*args, **kwargs): ①
if not hasattr(cls,'_inst'):
print(cls)
cls._inst = super(Singleton, cls).__new__(cls) ②
return cls._inst ②
如果Python3的写法跟Python2写法一样,那么倒数第二行会报错"TypeError: object() takes no parameters"
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