如何将 class 属性的未知长度列表中的每个项目打印为 python 中的字符串？

Question

我有一个 class（学生），具有不同的属性，例如学生 ID、地址和课程。我的str方法为 class returns 用户输入的所有信息。但是，对于列表的属性，例如课程，打印出信息的位置而不是实际信息.这是代码（抱歉有点长，有一堆classes）：

class Person:

    __name = None
    __age = None
    __address = None

    def __init__(self, name, age=0, address=None):
        self.set_name(name)
        self.set_age(age)
        self.set_address(address)
  
    def __str__(self):
        return 'Name: ' + self.__name + '\n' + \
               'Age: ' + str(self.__age) + '\n' + \
               'Address: ' + str(self.__address)

    def set_name(self, name):
        self.__name = name    

    def get_name(self):
        return self.__name

    def set_age(self, age):
        self.__age = age

    def get_age(self):
        return self.__age

    def set_address(self, address):
        self.__address = address

    def get_address(self):
        return self.__address

class Student(Person):

    def __init__(self, name, studentID= None, age= 0, address= None):
        super(Student, self).__init__(name, age, address)
        self.set_studentID(studentID)
        self.__courses =[]
    
    def __str__(self):
    
        result = Person.__str__(self)
        result += '\nStudent ID:' + self.get_studentID()
        for item in self.__courses:
            result += '\n   ' + str(item)
        return result
            
    def set_studentID(self, studentID):
        if isinstance(studentID, str) and len(studentID.strip()) > 0:
            self.__studentID = studentID.strip()
        else:
            self.__studentID = 'NA'

    def get_studentID(self):
        return self.__studentID   

    def add_course(self, course):
        print('in add_course')
        self.__courses.append(course)
 
    def get_courses(self):
        for i in range(len(self.__courses)):
            return self.__courses[i]    

class Course:

    __courseName = None
    __dept = None
    __credits = None

    def __init__(self, courseName, dept= 'GE', credits= None):
        self.set_courseName(courseName)
        self.set_dept(dept)
        self.set_credits(credits)
    
    def __str__(self):
        return self.get_courseName() + '/' + self.get_dept() + '/' + str(self.get_credits())

    def set_courseName(self, courseName):
        if isinstance(courseName, str) and len(courseName.strip()) > 0:
            self.__courseName = courseName.strip()
        else:
            print('ERROR: Name must be a non-empty string')
            raise TypeError('Name must be a non-empty string')

    def get_courseName(self):
        return self.__courseName

    def set_dept(self, dept):
        if isinstance(dept, str) and len(dept.strip()) > 0:
            self.__dept = dept.strip()
        else:
            self.__dept = "GE"

    def get_dept(self):
        return self.__dept

    def set_credits(self, credits): 
        if isinstance(credits, int) and credits > 0:
            self.__credits = credits
        else:
            self.__credits = 3

    def get_credits(self):
        return self.__credits

students = []

def recordStudentEntry():   
    
    name = input('What is your name? ')
    age = input('How old are you? ')
    studentID= input('What is your student ID? ')
    address = input('What is your address? ')
    s1 = Student(name, studentID, int(age), address)
    students.append(s1)
    s1.add_course(recordCourseEntry())
    print('\ndisplaying students...')
    displayStudents()
    print()        

        
def recordCourseEntry():
    courses = []
    for i in range(2):
        courseName = input('What is the name of one course you are taking? ')
        dept = input('What department is your course in? ')
        credits = input('How many credits is this course? ')
        c1 = Course(courseName, dept, credits)
        print(c1)
        courses.append(c1)
  
    displayCourses(courses)
    return courses
    
def displayCourses(courses):
    print('\ndisplaying courses of student... ')
    for c in range(len(courses)):
        print(courses[c])
    
def displayStudents():
    for s in range(len(students)):
        print()
        print(students[s])

recordStudentEntry()

上面的代码是这样打印出 'displaying students...' 部分的：

displaying students...

Name: sam
Age: 33
Address: 123 st
Student ID:123abc
   [<__main__.Course object at 0x000002BE36E0F7F0>, <__main__.Course object at 
0x000002BE36E0F040>]

我知道它正在打印位置，因为我需要在列表中建立索引。但是，列表的长度每次都会不同。通常如果我想索引一个列表，例如，打印一个名字列表，我会这样做：

listOfNames = ['sam', 'john', 'sara']
for i in range(len(listOfNames)):
    print(listOfNames[i])

或

listOfNames = ['sam', 'john', 'sara']
for i in listOfNames:
    print(i)

（不确定这两种方式之间是否存在差异，因为它们的打印方式相同:)

sam
john
sara

如何在我的 class 的 str 方法中编写类似索引到列表技术的内容，以便它打印信息而不是位置？

Answer 1

最好遵守 Python 的标准约定，例如命名具有单下划线而不是双下划线的对象的私有属性。后者保留用于 Python “内部”属性和方法。此外，约定使用 get/set 方法的对象的对象属性，不是 class 属性。这将使您更容易检查您的对象，同时仍然保持数据隐藏。示例：

class Course:
    def __init__(self, courseName, dept= 'GE', credits= None):
        self._courseName = None
        self._dept = None
        self._credits = None
        self.set_courseName(courseName)
...

关于为什么课程没有按照您预期的方式打印出来的问题根源于您对录音进行编程的方式存在编程错误当然。在recordCourseEntry()中，你录制了两门课程并把它们在列表中。但是，您使用方法将其传递给 Student 对象一次用于一门课程。我建议的修复方法是：

...
    # s1.add_course(recordCourseEntry())
    courses = recordCourseEntry()
    for course in courses:
        s1.add_course(course)
...

这可能足以让您继续前进。我得到的示例输出是：

Name: Virtual Scooter
Age: 33
Address: 101 University St.
Student ID:2021
   ff/GE/3
   gg/GE/3

如何将 class 属性的未知长度列表中的每个项目打印为 python 中的字符串？

How can I print each item in an unknown length list that is a class attribute as a string in python?

python

class-attributes