python - 添加一个列表类

Question

class Course:
    ''' 
    A class representing a course offering that includes the following
    information about the course: subject, course number, section,
    enrolment cap, lecture days, lecture start time, lecture duration 
    in minutes, and unique student numbers of the students enroled.
    If lectures occur on multiple days, they will all start at the same time.
    '''

    def __init__(self, subject, number, section, cap, days, start_time, dur):
        '''
        returns a new Course object with no students enroled, given
           the subject, number, section, cap, days, start_time, and dur
        __init__: Str Nat Nat Nat Str Time Nat -> Course
        requires: number is a 3-digit number, section > 0, cap > 0,
           days is string containing substrings representing the days
           of the week 'M', 'T', 'W', 'Th', 'F', where if the course is
           offered on more than one day, the days appear in order and
           are separated by a single dash. For example, 'M-T-Th'
           indicates the course is offered on Monday, Tuesday, and Th.
        '''
        self.subject = subject
        self.number = number
        self.section = section
        self.cap = cap
        self.days = days
        self.start_time = start_time
        self.dur = dur

    def add_student(self, student_id):
        '''
        adds a student to the course enrolment if there is room in the course
           if the number of students enroled already matches the 
           enrolment cap, then print the message "Course full"
           if the student is already enroled in the course, the there is no 
           change to the Course object, and the message "Previously enroled"
           is printed.
        add_student: Course Nat -> None
        Effects: Mutates self. May print feedback message.
        '''
        pass            

对于方法 add_student，如果它不在 init 方法中，我将如何实现一个列表(不能将其添加到初始化方法中)？该列表需要与对象相关联，以便稍后我可以从该列表中删除学生。

Answer 1

您可以将其添加到 __new__ 方法中:

class Course:
    def __new__(cls, *args, **kwargs):
        course = super(Course, cls).__new__(cls)
        course.students = []
        return course