带有排除类型的 TypeVar 的 Python 类型注释

Question

我试图用@overload不同的方式来传达调用函数的不同方式，但是在代码中用简单的else语句轻松传达的内容在类型注释中是不可能的。如果没有“else”，MyPy（正确地）会抱怨重载版本不匹配（例如，请参见下面的代码段）。

error: Overloaded function signatures 1 and 2 overlap with incompatible return types

我是否正确理解此问题没有好的解决方案？

例如。这是一个简单的例子：

ListOrTuple = TypeVar("ListOrTuple", List, Tuple)
# unfortunately, typing doesn't support "anything else" at the moment
# https://github.com/python/typing/issues/599#issuecomment-586007066
AnythingElse = TypeVar("AnythingElse")
# what I would like to have is something like AnythingElse= TypeVar("AnythingElse", Not[List,Tuple])

@overload
def as_list(val: ListOrTuple) -> ListOrTuple:
    ...

@overload
def as_list(val: AnythingElse) -> List[AnythingElse]:
    ...

def as_list(val):
    """Return list/tuple as is, otherwise wrap in a list

    >>> as_list("test")
    ['test']
    """
    return val if isinstance(val, (list, tuple)) else [val]

Answer 1

这是我的解决方法。它对我来说效果很好，但我一点也不喜欢它。

# attempt to list all the "other" possible types
AnythingElse = TypeVar("AnythingElse", Set, Mapping, type, int, str, None, Callable, Set, Deque, ByteString)
ListOrTuple = TypeVar("ListOrTuple", List, Tuple, Sequence)


@overload
def as_list(val: ListOrTuple) -> ListOrTuple:
    ...

@overload
def as_list(val: AnythingElse) -> List[AnythingElse]:
    ...

def as_list(val):
    """Return list/tuple as is, otherwise wrap in a list

    >>> as_list("test")
    ['test']
    """
    return val if isinstance(val, (list, tuple)) else [val]