在我的多类示例中如何修复此错误？

Question

class Students: #class is called Students
    
    def__init__(self, name, age, grade): #constructor for self, name, and age, for Students
    
    self.name = name
    self.age = age
    self.grade = grade
    
    def get_grade(self):
        
        return self.grade
    
class Course: #this class is called Course
    
    def__init__(self, name, max_students): #constructor to get name of Course and max number of students in Course
        
        self.name = name
        self.max_students = max_students
        self.students[]
    
    def add_student(self, student): #code to add students into course
        
        if len(self.students) < max_students:
            
            self.students.append(student) #if theres less students than the max number of students for Course, then append into course until it reaches max number of students
            return True
        return False
    
    def get_average_grade(self): #code to find the average
       pass

s1 = Student("Sam", 19, 78) #s1 is now accessing the Student class. Name, age and grade
s2 = Student("Bam", 19, 58)
s3 = Student("Pam", 19, 48)

course = Course("English", 2) #course is now accessing the Course class.Name of course and max number of students for course.
course.add_student(s1)
course.add_student(s2) #using add_student attribute in Course class to add students into course
print(course.add_student) #printing the result

请详细回答，因为我是初学者。谢谢。

我做错了什么？我怎样才能更有效率？ 我怎样才能防止这个错误发生？

Answer 1

您的代码存在多个问题：

1. 您的课程名为

   Students

   但您正在初始化

   Student

   （末尾缺少“s”）

2. print(course.add_student)

   尝试打印方法

   add_student()

   本身，而不是方法返回的内容。您需要使用参数调用该方法：

   print(course.add_student(s1))

3. add_student()

   方法返回一个布尔值，因此您的打印语句将打印

   True

   。这在技术上并不是不正确的，但可能不是您想要的。如果您想查看学生是否已成功添加，您可以检查该课程现在是否有两名学生：

   print(len(course.students))

4. 在

   add_student()

   中的 if 语句中，您需要与

   self.max_students

   进行比较，而不是与

   max_students

   进行比较

5. 在

   Course

   内，您没有正确初始化

   self.students

   ，您缺少等号。应该是这样的：

   self.students = []

   。这就是导致您出现错误消息的原因。

这是代码的清理版本：

class Students:
    def __init__(self, name, age, grade):
        self.name = name
        self.age = age
        self.grade = grade

    def get_grade(self):
        return self.grade

class Course: 
    def __init__(self, name, max_students):
        self.name = name
        self.max_students = max_students
        self.students = []

    def add_student(self, student): 
        if len(self.students) < self.max_students:
            self.students.append(student)
            return True
        return False

    def get_average_grade(self):
        pass

s1 = Students("Sam", 19, 78)
s2 = Students("Bam", 19, 58)
s3 = Students("Pam", 19, 48)

course = Course("English", 2)
print(len(course.students))  # You haven't added students yet, so this will print 0

result1 = course.add_student(s1)
result2 = course.add_student(s2)
result3 = course.add_student(s3) # This will be false and no student will be added since the max_student limit is exceeded

print(result1)
print(result2)
print(result3)

print(len(course.students)) # Now you have two students in your course