Class 属性和实例属性

Question

I am trying to learn the difference between the instance attributes and class attributes and attributes. I have the code below and I am trying to distinguish these factors.

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()

From what I understood the attributes would be: firstname,lastname,ucid,department,nationality,courses But I do not know what instance attributes and class attributes would be.

Answer 1

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

there should be two attributes, class attribute , instance attribute . or instance attribute & none-instance attribute for convenience.

instance attribute

• these are things activated only when __init__ has been called.
• you can only access thenm after Class is initialized, which commonly seen as self.xxx .
• and methods in class with self as its first parameter(normally), these functions are instance methods, and you can only access after you initialized the Class.
• and methods in class with @property deco, they are instance attributes

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 or static attribute , whatever you call it

• these things stay activated along with Class.
• which means you can access them whenever you need to, like __init__ , even in __new__ .
• they can be called by both Class and instance .

common seen class attribute 

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

there is something else you may should know, class method , which stay activated along with Class but the difference is class method can't be called by instance but only Class. example here

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

Conclusion

"class attribute" can be called by both instance and Class

"instance attribute" can only called by instance.