如何打印基类中父类的实例？

Question

当我将类继承到Sports中并在init方法中定义值时，我可以打印类Student的名称。 但我不知道如何打印创建学生班级时给出的姓名，而不在体育课中定义姓名

当我注释掉Student.__init__(self, 1, "name1", "addr1", 123456789, "std2@gmail.com", 1, 2021, "english") 当创建对象时，我想打印这些值

class Student:
    def __init__(self, sid, name, addr, phno, mailid, sec, year, sub):
        self.sid = sid
        self.name = name
        self.addr = addr
        self.phno = phno
        self.mailid = mailid
        self.sec = sec
        self.year = year
        self.sub = sub

    def printStudent(self):
        print("name",self.name,"sid",self.sid,"sec",self.sec,"year",self.year,"sub",
              self.sub, "address",self.addr,"mailid",self.mailid,"phno",self.phno)


class Sports(Student):
    def __init__(self, nofsports, nofawards):
        Student.__init__(self, 1, "name1", "addr1", 123456789, "std2@gmail.com", 1, 2021,
                         "english")
        self.nofsports = nofsports
        self.nofawards = nofawards

    def printSports(self):
        print("name", self.name)


s1 = Student(2,"name2","addr2",1221232332,"std1@gmail.com",1,2020,"math")

s2 = Sports(2, 2)
s2.printSports()

当我注释掉Student.__init__(self, 1, "name1", "addr1", 123456789, "std2@gmail.com", 1, 2021, "english") 当创建对象时，我想打印这些值

顺便说一句，我正在学习继承和python新手，我不明白为什么python不能像我继承的那样打印Student类的实例，可能是因为它不是class属性？请让我知道

Answer 1

通常，子类__init__方法获取其超类的所有参数，以及子类需要的任何附加参数。然后它可以将公共参数传递给超类的__init__方法

class Sports(Student):
    def __init__(self, sid, name, addr, phno, mailid, sec, year, sub, nofsports, nofawards):
        super().__init__(sid, name, addr, phno, mailid, sec, year, sub)
        self.nofsports = nofsports
        self.nofawards = nofawards

    def printSports(self):
        print("name", self.name)

s2 = Sports(1, "name1", "addr1", 123456789, "std2@gmail.com", 1, 2021, "english", 2, 2)

Answer 2

    class Student():

    _instance = None

    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            print("creating new object")
            cls._instance = super(Student, cls).__new__(cls)
        return cls._instance

    def __init__(self, sid, name, addr, phno, mailid, sec, year, sub):
        self.sid = sid
        self.name = name
        self.addr = addr
        self.phno = phno
        self.mailid = mailid
        self.sec = sec
        self.year = year
        self.sub = sub

    def printStudent(self):
        print("name",self.name,"sid",self.sid,"sec",self.sec,"year",self.year,"sub",
              self.sub, "address",self.addr,"mailid",self.mailid,"phno",self.phno)


class Sports(Student):
    def __init__(self, nofsports, nofawards, sid, name, addr, phno, mailid, sec, year, sub):
        super().__init__(sid, name, addr, phno, mailid, sec, year, sub)
        self.nofsports = nofsports
        self.nofawards = nofawards

    def printSports(self):
        print("name", self.name)


s2 = Sports(2,2,2,"name2","addr2",1221232332,"std1@gmail.com",1,2020,"math")
s2.printSports()
s3 = Sports(2,2,2,"name3","addr3",56516516,"std3@gmail.com",1,2020,"phy")
s3.printStudent()
s2.printStudent()

***

creating new object
name name2
name name3 sid 2 sec 1 year 2020 sub phy address addr3 mailid std3@gmail.com phno 56516516
name name3 sid 2 sec 1 year 2020 sub phy address addr3 mailid std3@gmail.com phno 56516516

***

希望这将帮助您了解更多，创建子类的对象而不是创建基类的对象。此外，基类被设置为单例类，因此只存在一个对象