mypy 忽略常规方法中的错误，但在 __init__ 中引发错误答案

【问题标题】：mypy ignoring error in regular method but raising an error in __init__mypy 忽略常规方法中的错误，但在 __init__ 中引发错误
【发布时间】：2022-01-01 19:42:40
【问题描述】：

我有一个如下所示的类：

from typing import Optional
import numpy as np

class TestClass():
    def __init__(self, a: Optional[float] = None):
        self.a = np.radians(a)

这会返回错误Argument 1 to "__call__" of "ufunc" has incompatible type "Optional[float]"; expected "Union[Union[int, float, complex, str, bytes, generic], Sequence[Union[int, float, complex, str, bytes, generic]], Sequence[Sequence[Any]], _SupportsArray]"

但是，即使它本质上做同样的事情，以下类也没有问题地通过：

from typing import Optional
import numpy as np

class TestClass():
    def __init__(self, a: Optional[float] = None):
        self.a = a

    def test(self):
        b = np.radians(self.a)

使用np.radians(None) 也没有任何影响。如何让 mypy 认识到这也会导致错误？

【问题讨论】：

标签： python type-hinting mypy

【解决方案1】：

你定义了一个未经检查的函数，因为你没有注释任何东西，mypy *不输入检查test，只需添加一个注释：

from typing import Optional
import numpy as np

class TestClass:
    def __init__(self, a: Optional[float] = None):
        self.a = a

    def test(self) -> None:
        b = np.radians(self.a)

你得到了预期的错误

(py39) jarrivillaga-mbp16-2019:~ jarrivillaga$ mypy test_typing.py
test_typing.py:9: error: Argument 1 to "__call__" of "ufunc" has incompatible type "Optional[float]"; expected "Union[Union[int, float, complex, str, bytes, generic], Sequence[Union[int, float, complex, str, bytes, generic]], Sequence[Sequence[Any]], _SupportsArray]"
Found 1 error in 1 file (checked 1 source file)

还要注意，如果你使用了mypy --strict，它就会被抓到：

(py39) jarrivillaga-mbp16-2019:~ jarrivillaga$ mypy --strict test_typing.py
test_typing.py:8: error: Function is missing a return type annotation
test_typing.py:8: note: Use "-> None" if function does not return a value
test_typing.py:9: error: Argument 1 to "__call__" of "ufunc" has incompatible type "Optional[float]"; expected "Union[Union[int, float, complex, str, bytes, generic], Sequence[Union[int, float, complex, str, bytes, generic]], Sequence[Sequence[Any]], _SupportsArray]"
Found 2 errors in 1 file (checked 1 source file)

【讨论】：