__init__、__new__方法详解

__init__详解

class Dog(object):

    def __init__(self):

        print('init方法')

    def __del__(self):

        print('del方法')

    def __str__(self):

        print('str方法')

    def __new__(cls, *args, **kwargs):

        print('new方法')

        return object.__new__(cls)

xtq=Dog()

'''

相当于要做三件事：

1、调用__new__方法来创建对象，然后找一个变量来接收__new__的返回值，这个返回值表示创建出来的对象的引用

2、__init__（刚创建出来的引用）

3、返回对象的引用

在 C++、java中的构造方法用来创建、初始化

在python中实际由 __new__、__init__ 来创建、初始化，所以init不等价于构造方法

'''

init方法为对象定制自己独有的特征

#方式一、为对象初始化自己独有的特征

class People:

    country='China'

    x=1

    def run(self):

        print('----->', self)

# 实例化出三个空对象

obj1=People()

obj2=People()

obj3=People()

# 为对象定制自己独有的特征

obj1.name='egon'

obj1.age=18

obj1.sex='male'

obj2.name='lxx'

obj2.age=38

obj2.sex='female'

obj3.name='alex'

obj3.age=38

obj3.sex='female'

# print(obj1.__dict__)

# print(obj2.__dict__)

# print(obj3.__dict__)

# print(People.__dict__)

#方式二、为对象初始化自己独有的特征

class People:

    country='China'

    x=1

    def run(self):

        print('----->', self)

# 实例化出三个空对象

obj1=People()

obj2=People()

obj3=People()

# 为对象定制自己独有的特征

def chu_shi_hua(obj, x, y, z): #obj=obj1,x='egon',y=18,z='male'

    obj.name = x

    obj.age = y

    obj.sex = z

chu_shi_hua(obj1,'egon',18,'male')

chu_shi_hua(obj2,'lxx',38,'female')

chu_shi_hua(obj3,'alex',38,'female')

#方式三、为对象初始化自己独有的特征

class People:

    country='China'

    x=1

    def chu_shi_hua(obj, x, y, z): #obj=obj1,x='egon',y=18,z='male'

        obj.name = x

        obj.age = y

        obj.sex = z

    def run(self):

        print('----->', self)

obj1=People()

# print(People.chu_shi_hua)

People.chu_shi_hua(obj1,'egon',18,'male')

obj2=People()

People.chu_shi_hua(obj2,'lxx',38,'female')

obj3=People()

People.chu_shi_hua(obj3,'alex',38,'female')

# 方式四、为对象初始化自己独有的特征

class People:

    country='China'

    x=1

    def __init__(obj, x, y, z): #obj=obj1,x='egon',y=18,z='male'

        obj.name = x

        obj.age = y

        obj.sex = z

    def run(self):

        print('----->', self)

obj1=People('egon',18,'male') #People.__init__(obj1,'egon',18,'male')

obj2=People('lxx',38,'female') #People.__init__(obj2,'lxx',38,'female')

obj3=People('alex',38,'female') #People.__init__(obj3,'alex',38,'female')

# __init__方法

# 强调：

#   1、该方法内可以有任意的python代码

#   2、一定不能有返回值

class People:

    country='China'

    x=1

    def __init__(obj, name, age, sex): #obj=obj1,x='egon',y=18,z='male'

        # if type(name) is not str:

        #     raise TypeError('名字必须是字符串类型')

        obj.name = name

        obj.age = age

        obj.sex = sex

    def run(self):

        print('----->', self)

# obj1=People('egon',18,'male')

obj1=People(3537,18,'male')

# print(obj1.run)

# obj1.run() #People.run(obj1)

# print(People.run)