创建实例时，python会自动调用类中的__init__方法，以隐性地为实例提供属性

__init__ 方法被称为构造器
如果类中没有定义__init__方法，实例创建之初仅是一个简单的名称空间
class Myclass：
a ="hello world"
def __init__(self,x)
self.name=x
x =Myclass("list")
y = Myclass("abc")　重载构造器(When an instance is created, the python automatically calls the __init__ method in the class to provide the attributes recessive for the instance



The __init__ method is called a constructor

If the __init__ method is not defined in the class, a simple namespace is only a simple namespace at the beginning of the instance creation

Class Myclass:

A = "Hello world"

Def __init__ (self, x)

Self.name=x

X =Myclass ("list")

Y = Myclass ("ABC") overloaded constructor)