查看“Py3 oop”的源代码

[[category:python]] 
=2024=
== 类(Class)与对象(Object) ==
<pre>
class Student:
    def __init__(self,name,score):
        self.name = name 
        self.score = score 

    def show(self):
        print("Name: {}. Score: {}".format(self.name,self.score))

student1 = Student("evan",100)
print(student1)
student1.show()

# ➜  tmp py3  clas.py
# <__main__.Student object at 0x7f007c9e9890>
# Name: evan. Score: 100
</pre>
== 类变量(class variables)与实例变量（instance variables）==
<pre>
class Student:

    # number属于类变量，定义在方法外，不属于具体实例
    number =0
    def __init__(self,name,score):
        self.name = name 
        self.score = score 

        # number = number + 1
        ## number属于类变量，定义在方法外，不属于具体实例

        Student.number = Student.number + 1

    def show(self):
        print("Name: {}. Score: {}".format(self.name,self.score))

student1 = Student("evan",100)
print(student1)
student1.show()

print(Student.number)
print(student1.__class__.number)

# ➜  tmp py3  clas.py
# <__main__.Student object at 0x7fb907ed9890>
# Name: evan. Score: 100
# 1
# 1
</pre>


==类方法(Class method)==
<pre>
class Student:

    # number属于类变量，定义在方法外，不属于具体实例
    number =0
    def __init__(self,name,score):
        self.name = name 
        self.score = score 

        # number = number + 1
        ## number属于类变量，定义在方法外，不属于具体实例

        Student.number = Student.number + 1

    def show(self):
        print("Name: {}. Score: {}".format(self.name,self.score))

    # 定义类方法，打印学生的数量 属于类的方法不使用self参数， 而使用参数cls，代表类本身。另外习惯上对类方法我们会加上@classmethod的修饰符做说明
    @classmethod 
    def total(cls):
        print("Total: {0}".format(cls.number))

student1 = Student("evan",100)
Student.total() # Total: 1
</pre>

== 类的私有属性(private attribute)和私有方法(private method) ==
<pre>
class Student:

    # number属于类变量，定义在方法外，不属于具体实例
    number =0
    def __init__(self,name,score):
        self.name = name 
        self.__score = score 

        # number = number + 1
        ## number属于类变量，定义在方法外，不属于具体实例

        # Student.number = Student.number + 1

    def show(self):
        print("Name: {}. Score: {}".format(self.name,self.__score))

    # 定义类方法，打印学生的数量 属于类的方法不使用self参数， 而使用参数cls，代表类本身。另外习惯上对类方法我们会加上@classmethod的修饰符做说明
    # @classmethod 
    # def total(cls):
    #     print("Total: {0}".format(cls.number))



student1 = Student("evan",100)

student1.show() # Name: evan. Score: 100
student1.__score  ## 打印出错，该属性不能从外部访问


class Student:

    # number属于类变量，定义在方法外，不属于具体实例
    number =0
    def __init__(self,name,score):
        self.name = name 
        self.__score = score 

    # 利用property装饰器把函数伪装成属性
    @property
    def score(self):
        print("Name: {}. Score: {}".format(self.name,self.__score))

    # 定义类方法，打印学生的数量 属于类的方法不使用self参数， 而使用参数cls，代表类本身。另外习惯上对类方法我们会加上@classmethod的修饰符做说明
    # @classmethod 
    # def total(cls):
    #     print("Total: {0}".format(cls.number))



student1 = Student("evan",100)
#注意： 一旦给函数加上一个装饰器@property,调用函数的时候不用加括号就可以直接调用函数了

student1.score # Name: evan. Score: 100



</pre>

== 类的继承(Inheritance) ==
<pre>
class SchoolMember:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def tell(self):
        print("Name: {}, Age: {}".format(self.name, self.age),end="")

class Teacher(SchoolMember):
    def __init__(self,name,age,salary):
        SchoolMember.__init__(self,name,age)# 利用父类进行初始化
        self.salary = salary 

    def tell(self):
        SchoolMember.tell(self)
        print("Salary: {}".format(self.salary))

class Student(SchoolMember):

    def __init__(self,name,age,score):
        SchoolMember.__init__(self,name,age)
        self.__score = score 

    def tell(self):
        SchoolMember.tell(self)
        print(", Score: {}".format(self.__score))


teacher1 = Teacher("Alice",25,30000)

student1 = Student("evan",30,100)

teacher1.tell()
student1.tell()


# ➜  tmp py3  clas.py
# Name: Alice, Age: 25Salary: 30000
# Name: evan, Age: 30, Score: 100
# ➜  tmp 

</pre>

== super()关键字调用父类方法 ==
<pre>
# 创建子类学生Student
class Student(SchoolMember):

    def __init__(self, name, age, score):
        super().__init__(name, age)
        self.score = score
    
    def tell(self):
        super().tell() # 等同于 SchoolMember.tell(self)
        print('score: {}'.format(self.score))
</pre>

== 类 ==
<pre>

</pre>

=类对象=
<pre>

#!/usr/bin/python3
 
class MyClass:
    """一个简单的类实例"""
    i = 12345
    def f(self):
        return 'hello world'
 
# 实例化类
x = MyClass()
 
# 访问类的属性和方法
print("MyClass 类的属性 i 为：", x.i)
print("MyClass 类的方法 f 输出为：", x.f())


#
以上创建了一个新的类实例并将该对象赋给局部变量 x，x 为空的对象。

执行以上程序输出结果为：

MyClass 类的属性 i 为： 12345
MyClass 类的方法 f 输出为： hello world
</pre>

=see also=
[https://www.runoob.com/python3/python3-class.html Python3 面向对象]

== __init__() 的特殊方法（构造方法）==
<pre>
类有一个名为 __init__() 的特殊方法（构造方法），该方法在类实例化时会自动调用


#!/usr/bin/python3
 
class Complex:
    def __init__(self, realpart, imagpart):
        self.r = realpart
        self.i = imagpart
x = Complex(3.0, -4.5)
print(x.r, x.i)   # 输出结果：3.0 -4.5


</pre>