Class 属性和实例属性

Question

我正在尝试了解实例属性与class属性和属性之间的区别。我有下面的代码，我正在尝试区分这些因素。

class Student:
    firstname = ""
    lastname = ""
    ucid = ""
    department = ""
    nationality = ""
    courses = {}

    def __init__(self, fname, lname, ucid, dept, n):
        self.firstname = fname
        self.lastname = lname
        self.ucid = ucid
        self.department = dept
        self.nationality = n
        self.courses = {}

    def setName(self, fname, lname):
        self.firstname = fname
        self.lastname = lname

    def setDepartment(self, d):
        self.department = d

    def setUcid(self, u):
        self.ucid = u

    def setNationality(self, n):
        self.nationality = n

    def addCourse(self, coursename, gpa):
        self.courses[coursename] = gpa

    def printAll(self):
        print("The name of the student is ", self.firstname, self.lastname)
        print("nationality and UCID: ", self.nationality, self.ucid)
        print("Department: ", self.department)
        print("Result: ")
        for key in self.courses.keys():
            print(key, self.courses[key])

        print("--------------------\n")

s1=Student("Beth","Bean","30303","Computer Science","International")
s1.addCourse("SCIENCE",3.75)
s1.printAll()
s2=Student("Mac","Miller","30303","Envr Science","American")
s2.addCourse("MATH",4.00)
s2.printAll()

据我了解，属性是：firstname,lastname,ucid,department,nationality,courses 但我不知道 instance attributes 和 class attributes 是什么。

Answer 1

I am trying to learn the difference between the instance attributes and class attributes and attributes.

应该有两个属性，class attribute，instance attribute。或 instance attribute&none-instance attribute 为了方便起见。

`instance attribute`

这些是仅在调用 __init__ 时才会激活的东西。
只有在Class初始化后才能访问thenm，一般见self.xxx.
和class中的方法以self为第一个参数（通常），这些函数是实例方法，只有在初始化Class后才能访问。
和class中的方法与@property deco，它们是实例属性

common seen instance attribute 

class Name(object):
   def __init__(self):
        self.age = 100
   def func(self):
       pass
   @property
   def age(self):
       return self.age

`class attribute`

non-instance attribute 或 static attribute，无论你怎么称呼它

这些东西与 Class 一起保持激活状态。
这意味着您可以随时访问它们，例如 __init__，即使在 __new__.
它们可以被 Class 和 instance 调用。

common seen class attribute 

class Name(object):
   attr = 'Im class attribute'

还有一些你可能应该知道的东西，class method，它与 Class 一起保持激活，但不同之处在于 class method 不能被实例调用，只能被 Class。这里的例子

class Name(object)
   attr = 'Im class attribute'
   @classmethod
   def get_attr(cls):
       return cls.attr

结论

"class属性"可以被实例和Class

调用

“实例属性”只能被实例调用。

Class 属性和实例属性

Class Attributes and Instance Attributes

python

function

oop

attributes

instance-variables

`instance attribute`

`class attribute`

结论