Python 输入 class 实例属性作为输入参数的副本

Question

当使用输入 Python 是否足够时：

class Something:
    def __init__(self, arg1: str, arg2: Union[str, int]):
        self.arg1 = arg1
        self.arg2 = arg2

或者所有的东西都应该打字？以下是否有优点并且是编码约定？

class Something:
    def __init__(self, arg1: str, arg2: Union[str, int]):
        self.arg1: str = arg1
        self.arg2: Union[str, int] = arg2

Answer 1

这取决于您的类型检查器的智能程度，但我希望所有当前的 Python 检查器都能够从第一种形式推断出 arg1 和 [= 的类型14=].

请注意，您缺少 return 类型注释，-> None:

class Something:
    def __init__(self, arg1: str, arg2: Union[str, int]) -> None:
        self.arg1 = arg1
        self.arg2 = arg2

例如，参见 mypy documentation on Class basics:

The mypy type checker detects if you are trying to access a missing attribute, which is a very common programming error. For this to work correctly, instance and class attributes must be defined or initialized within the class. Mypy infers the types of attributes:
class A:
    def __init__(self, x: int) -> None:
        self.x = x  # Aha, attribute 'x' of type 'int'

a = A(1)
a.x = 2  # OK!
a.y = 3  # Error: 'A' has no attribute 'y'

（大胆强调我的）。

否则，我更喜欢将实例属性注释放在 class 级别，这样它们更容易被其他开发人员阅读：

class Something:
    arg1: str
    arg2: Union[str, int]

    def __init__(self, arg1: str, arg2: Union[str, int]) -> None:
        self.arg1 = arg1
        self.arg2 = arg2

在这里，这会导致您不得不重复自己，但您可以考虑 using the dataclasses module 避免这种情况。

Python 输入 class 实例属性作为输入参数的副本

Python typing of class instance attributes as copies of input args

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