如何将Python父子类对象的属性写入TXT文件？

我编写了Python父子类程序：父类Staff接收4个字符串输入，子类TeachingStaff继承自Staff并接收6个字符串输入。尝试将用户输入生成的类对象转成字符串写入TXT文件时，文件里只显示对象的内存地址（比如<__main__.TeachingStaff object at 0x000001EAE84A1390>），不知道怎么把属性内容写入文件。原代码如下：

#define parent class
class Staff:
    def __init__(self, fname, lname, dob, department):
        self.fname = fname
        self.lname = lname
        self.dob = dob
        self.department = department

#define print function to print the parent class object
def printsf(self):
    print(self.fname, self.lname, self.dob, self.department)

#define child class
class TeachingStaff(Staff):
    def __init__(self, fname, lname, dob, department, discipline, licenseNumber):
        super().__init__(fname, lname, dob, department)
        self.discipline = discipline
        self.licenseNumber = licenseNumber

#define print function to print the child class object
def printtsf(self):
    print(self.fname, self.lname, self.dob, self.department, self.discipline, self.licenseNumber)

staffDetails = open("staffDetails.txt", "a")  # open file for appending
teachingDetails = open("teachingDetails.txt", "a")  # open file for appending

loopdobInput = input("Enter the date of birth in the format DD/MM/YYYY:")
loopfnameInput = input("Enter first name:")
looplnameInput = input("Enter last name:")
loopdepartmentInput = input("Enter department name:")
loopdecisionInput = input("Is the staff member a teacher (Y/N?")
if loopdecisionInput == "y" or loopdecisionInput == "Y":
    loopdisiplineInput = input("Enter discipline:")
    looplicenceInput = input("Enter licence number:")
    loopteachingInput = TeachingStaff(loopdobInput, loopfnameInput, looplnameInput, loopdepartmentInput,
    loopdisiplineInput, looplicenceInput)
    loopteachingstr = str(loopteachingInput)
    teachingDetails.write(loopteachingstr)
else:
    loopstaffInput = Staff(loopdobInput, loopfnameInput, looplnameInput, loopdepartmentInput)
    loopstaffstr = str(loopstaffInput)
    staffDetails.write(loopstaffstr)

staffDetails.close()
teachingDetails.close()

解决方案 #

问题根源是Python默认的str()实现会返回对象的内存地址，需要在类中自定义__str__方法，让对象转字符串时输出属性内容。同时优化代码结构，用with语句简化文件操作：

1. 给父类Staff添加__str__方法，返回属性拼接的字符串
2. 给子类TeachingStaff添加__str__方法，复用父类逻辑并拼接子类特有的属性
3. 将外部打印函数改为类方法（符合面向对象规范）
4. 使用with语句自动管理文件，避免手动关闭遗漏

修改后的完整代码：

# 定义父类
class Staff:
    def __init__(self, fname, lname, dob, department):
        self.fname = fname
        self.lname = lname
        self.dob = dob
        self.department = department

    # 自定义__str__方法，返回属性内容
    def __str__(self):
        return f"{self.fname}, {self.lname}, {self.dob}, {self.department}"
    
    # 类内的打印方法
    def print_details(self):
        print(self.fname, self.lname, self.dob, self.department)

# 定义子类
class TeachingStaff(Staff):
    def __init__(self, fname, lname, dob, department, discipline, licenseNumber):
        super().__init__(fname, lname, dob, department)
        self.discipline = discipline
        self.licenseNumber = licenseNumber

    # 自定义子类的__str__方法
    def __str__(self):
        # 复用父类的__str__逻辑，拼接子类属性
        return f"{super().__str__()}, {self.discipline}, {self.licenseNumber}"
    
    # 子类的打印方法
    def print_details(self):
        print(self.fname, self.lname, self.dob, self.department, self.discipline, self.licenseNumber)

# 处理用户输入
loopdobInput = input("Enter the date of birth in the format DD/MM/YYYY:")
loopfnameInput = input("Enter first name:")
looplnameInput = input("Enter last name:")
loopdepartmentInput = input("Enter department name:")
loopdecisionInput = input("Is the staff member a teacher (Y/N)?")

if loopdecisionInput.lower() == "y":
    loopdisiplineInput = input("Enter discipline:")
    looplicenceInput = input("Enter licence number:")
    # 注意参数顺序：原代码中把dob放在了第一个，和类的__init__参数顺序不符，这里修正了
    loopteachingInput = TeachingStaff(loopfnameInput, looplnameInput, loopdobInput, loopdepartmentInput,
                                     loopdisiplineInput, looplicenceInput)
    # 调用自定义__str__方法转字符串，写入文件时加换行符分隔记录
    with open("teachingDetails.txt", "a") as teachingDetails:
        teachingDetails.write(str(loopteachingInput) + "\n")
else:
    loopstaffInput = Staff(loopfnameInput, looplnameInput, loopdobInput, loopdepartmentInput)
    with open("staffDetails.txt", "a") as staffDetails:
        staffDetails.write(str(loopstaffInput) + "\n")

关键说明 #

• __str__是Python特殊方法，调用str(obj)或打印对象时会自动触发，自定义后可返回指定格式的属性字符串
• super().__str__()复用父类的字符串生成逻辑，减少代码重复
• with语句会在代码块结束后自动关闭文件，比手动调用close()更安全
• 写入时添加\n换行符，让每条记录单独占一行，方便后续读取

内容的提问来源于stack exchange，提问作者Phillip Handfield