Python自定义类方法中打印self输出实例内存地址问题求解

问题原因 #

• 当你在f字符串中直接引用类实例self时，Python会自动调用实例的__str__方法获取字符串表示
• 你自定义的Customer类没有重写__str__方法，默认继承自object基类的__str__方法，返回值就是内存地址格式的字符串，所以出现了你看到的输出

修复步骤 #

在Customer类内部添加自定义的__str__方法，指定实例转换为字符串时的输出规则即可，修改后的完整代码如下：

class Customer:
    """The people who are going to be accessing this program"""
    
    def __init__(self, first, last, gender, age):
        self.first = first 
        self.last = last
        self.gender = gender
        self.age = age
    
    # 新增自定义__str__方法
    def __str__(self):
        # 你可以根据需求调整输出格式，这里输出用户全名
        return f"{self.first} {self.last}"
    
    def buying_something(self):
        """The customer is now buying something"""
        print(f"{self} is now buying something")
    def browsing(self):
        """The customer is now browsing something"""
        print(f"{self} is now browsing something")

customer_1 = Customer('John', 'Doe', 'Male', 20)
print(f"This customers name is {customer_1.first}")
print(f"This customers age is {customer_1.age}")
customer_1.buying_something()

修复后输出结果 #

This customers name is John
This customers age is 20
John Doe is now buying something

拓展说明 #

如果需要在调试场景下也能看到相同的可读表示，可以在类中额外添加一行__repr__ = __str__，让实例的正式表示和非正式字符串表示保持一致。

内容的提问来源于stack exchange，提问作者hilal123