class Course: courses = None def __init__(self, name, credit, time): self.name = name self.credit = credit self.time = time self.courses = [] def add_course(self,course): self.courses.append(course) def print_course(self): for course in self.courses: print(course.name) def choose_class(): print(''' 1.'Advanced Mathematics', 'credit:4', 'Monday 8:30-10:10')) 2.'College English', 'credit:3', 'Tuesday 2:30-4:10' 3.'Computer programming', 'credit:4', 'Wednesday 10:30-12:10' 4.'Computer Design', 'credit:3', 'Thursday 4:30-6:10''') ch = int(input('Please choose the class that you want:')) if ch == 1: Course.add_course('Advanced Mathematics') elif ch == 2: Course.add_course('College English') elif ch == 3: Course.add_course('Computer programming') elif ch == 4: Course.add_course('Computer Design')

这段代码有几个问题需要修正才能正确运行：

1. courses 属性应该是一个类属性，而不是实例属性，应该在类定义时初始化，而不是在 `__init__` 方法中定义。

2. `add_course` 方法需要传入一个 `Course` 类型的参数，而不是一个字符串。

3. `choose_class` 方法应该是一个静态方法或者类方法，而不是一个普通函数。

修改后的代码如下：

class Course:
    courses = [
        Course('Advanced Mathematics', 4, 'Monday 8:30-10:10'),
        Course('College English', 3, 'Tuesday 2:30-4:10'),
        Course('Computer programming', 4, 'Wednesday 10:30-12:10'),
        Course('Computer Design', 3, 'Thursday 4:30-6:10')
    ]

    def __init__(self, name, credit, time):
        self.name = name
        self.credit = credit
        self.time = time

    @classmethod
    def add_course(cls, course):
        cls.courses.append(course)

    @classmethod
    def print_courses(cls):
        for course in cls.courses:
            print(course.name)

    @staticmethod
    def choose_class():
        print(''' 
        1. Advanced Mathematics, credit:4, Monday 8:30-10:10
        2. College English, credit:3, Tuesday 2:30-4:10
        3. Computer programming, credit:4, Wednesday 10:30-12:10
        4. Computer Design, credit:3, Thursday 4:30-6:10
        ''')
        ch = int(input('Please choose the class that you want:'))
        if ch == 1:
            Course.add_course(Course('Advanced Mathematics', 4, 'Monday 8:30-10:10'))
        elif ch == 2:
            Course.add_course(Course('College English', 3, 'Tuesday 2:30-4:10'))
        elif ch == 3:
            Course.add_course(Course('Computer programming', 4, 'Wednesday 10:30-12:10'))
        elif ch == 4:
            Course.add_course(Course('Computer Design', 3, 'Thursday 4:30-6:10'))

这样，我们就可以通过调用 `Course.choose_class()` 方法来选择课程，调用 `Course.print_courses()` 方法来打印所有已选的课程了。