Python mypy type error with Union of callable and list of callable converted to list of callable

Question

参数hook可以是函数也可以是函数列表。如果它是一个函数，我会把它转换成一个列表，这样我以后就可以假设它是一个列表。

HookType = Union[Callable[[str], str], List[Callable[[str], str]]]

...

def __init__(
    ...
    hook: HookType = [],
):
    ...
    if type(hook) is not list:
        hook = [hook]
    self.hook: List[Callable[[str], str]] = hook

当我运行 mypy 我得到以下错误：

foo.py:54: error: List item 0 has incompatible type "Union[Callable[[str], str], List[Callable[[str], str]]]"; expected "Callable[[str], str]"
foo.py:57: error: Incompatible types in assignment (expression has type "Union[Callable[[str], str], List[Callable[[str], str]]]", variable has type "List[Callable[[str], str]]")
Found 4 errors in 1 file (checked 20 source files)

mypy不检测检查hook类型的条件吗？

我还应该提到我启用了一些 mypy 选项：

[mypy]
check_untyped_defs = true
disallow_incomplete_defs = true

Answer 1

这可以通过使用 isinstance 来“修复”（至少在 Pycharm 的静态检查器实现中）：

if not isinstance(hook, list):
    hook = [hook]

MyPy 比 Pycharm 更严格，但我希望它也能为 MyPy 修复它。 if type(x) is y 似乎会抛出类型检查器。

Python mypy type error with Union of callable and list of callable converted to list of callable

Python mypy type error with Union of callable and list of callable converted to list of callable

python

type-hinting

mypy