python - 使用继承编写 __repr__ 函数的正确方法

Question

我正在试验 OOP python，我不确定 __repr__ 函数继承。由于父类函数看起来像这样:

def __repr__(self):
    '''Returns representation of the object'''
    return("{}({!r})".format("Class name", self._param))

我想知道使用像下面这样的通用方法(也适用于 child 类(class))是否更好:

def __repr__(self):
    '''Returns representation of the object'''
    return("{}({!r})".format(self.__class__.__name__, self._param))

或者在每个类中重写该函数是否是一个好习惯。

此外，请忽略编码部分，因为我将其放在后面。

Answer 1

嗯 __repr__ 在 Python 的数据模型中有特殊意义:

object.__repr__(self)

Called by the repr() built-in function to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment). If this is not possible, a string of the form <...some useful description...> should be returned. The return value must be a string object. If a class defines __repr__() but not __str__(), then __repr__() is also used when an “informal” string representation of instances of that class is required.

This is typically used for debugging, so it is important that the representation is information-rich and unambiguous.

这意味着 __repr__ 返回的字符串应该可以用来创建另一个类似的对象。所以__repr__是经常需要覆盖的东西，不是因为 __class__.__name__但是因为必须在表示中捕获“状态”。

class A(object):
    def __init__(self, param):
        self._param = param

    def __repr__(self):
        '''Returns representation of the object'''
        return("{}({!r})".format(self.__class__.__name__, self._param))

那么你绝对应该覆盖 __repr__当您为 __init__ 添加参数时:

class B(A):
    def __init__(self, param1, param2):
        self._param = param1
        self._param2 = param2

    def __repr__(self):
        '''Returns representation of the object'''
        return("{}({!r})".format(self.__class__.__name__, self._param, self._param2))

但如果 __repr__父类(super class)仍然准确地“描述”子类，那么重载 __repr__ 就没有意义了。 :

class B(A):
     pass

---

然而，使用 self.__class__.__name__ 始终是一个不错的选择避免对类名进行硬编码，以防万一您或其他人对其进行子类化。