Python类：'int‘对象在my类中的函数中没有属性

Question

我是Python面向对象编程的新手。我在网上复制了这段代码，以便更好地了解OOP在Python中的工作方式。以下是代码：

class Student:

    def __init__(self, name, student_number):
        ## Student has-a name
        self.name = name
        ## Student has-a student number
        self.student_number = student_number
        ## Student has-many classes
        self.classes = []

    def enrol(self, course_running):
        ## Append the list, classes with variable course_running
        self.classes.append(course_running)
        ## Call course_running with the add_student function in a class
        course_running.add_student(self)

class Department:

    def __init__(self, name, department_code):
        ## Department has-a name
        self.name = name
        ## Department has-a code
        self.department_code = department_code
        ## Department has-many courses
        self.courses = {}

    def add_course(self, description, course_code, credits):
        self.courses[course_code] = Course(self, description, course_code, credits)
        return self.courses[course_code]

class Course:

    def __init__(self, description, course_code, credits, department):
        ## Course has-a description
        self.description = description
        ## Course has-a code
        self.course_code = course_code
        ## Course has-many credits
        self.credits = credits
        ## Course has-a deparmtnet
        self.department = department
        ## Adds the aforementioned course to the necessary DPT; it is usefull because
        ## it automatically adds this course to the DPT given in its parameter
        self.department.add_course(self)
        ## Course has-many runnings
        self.runnings = []

        def add_running(self, year):
            self.runnings.append(CourseRunning(self, year))
            return self.runnings[-1]

class CourseRunning:

    def __init__(self, course, year):
        ## CourseRunning has-a year
        self.course = course
        ## CourseRunning has-a year
        self.year = year
        ## CourseRunning has-many students
        self.students = []

    def add_student(self, student):
        self.students.append(student)

maths_dept = Department("Mathematics and Applied Mathemtics", "MAM")
mam1000w = maths_dept.add_course("Mathematics 1000", "MAM1000W", 1)
mam1000w_2013 = mam1000w.add_running(2013)

bob = Student("Bob", "Smith")
bob.enrol(mam1000w_2013)

然而，我不断地发现这些错误：

Traceback (most recent call last):
  File "ex42c.py", line 70, in <module>
    mam1000w = maths_dept.add_course("Mathematics 1000", "MAM1000W", 1)
  File "ex42c.py", line 30, in add_course
    self.courses[course_code] = Course(self, description, course_code, credits)
  File "ex42c.py", line 47, in __init__
    self.department.add_course(self)
AttributeError: 'int' object has no attribute 'add_course'

我将'int‘对象更改为'list’对象，然后改为'str‘对象，但它们产生了类似的错误。当我删除整数和所有‘信用’变量时，'course_code‘变量和str“MAM1000W”变量发生了相同的错误。基本上，我想了解为什么不能将这些参数传递给函数。

提前谢谢。

Answer 1

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删除上述内容( self.department.add_course(self))后，请取消以下部分：

def add_running(self, year):
    self.runnings.append(CourseRunning(self, year))
    return self.runnings[-1]

它对我有效，虽然我不确定这是否是你希望它工作的方式。

它以前不起作用，因为您试图在课程中使用Department的方法。部门只是一个Integer类型的论点，而不是您可能想要的department对象。同样的方法已经存在于Department类中了，为什么不只使用它呢？

第二部分是取消缩进add_running()函数，因为它是在init块中输入的。

我希望这能帮上忙。

Answer 2

第一个问题是，您将参数以错误的顺序传递给Course。

而不是self.courses[course_code] = Course(self, description, course_code, credits)

你需要self.courses[course_code] = Course(description, course_code, credits, self)

因为在您的Course.__init__中，它们按顺序排列：def __init__(self, description, course_code, credits, department)。

，然后是，您有一个递归循环，其中add_course函数由Course __init__调用，在add_course中创建Course时调用.以此类推。

除了，也不会发生这种情况，因为调用Course.__init__中的self.department.add_course(self)缺少了Department.add_course - course_code和credits所需的两个参数。

简而言之:你在这里有很多问题。我们可以修复其中的大多数，但是关于递归调用add_course的决定将要求您决定是希望部门添加课程，还是让课程将自己添加到部门中。