如何注释 f(*params)？
How can I annotate f(*params)?
我不知道如何正确注释这段代码：
from typing import Iterable
def f(*params: Iterable) -> str:
return ":".join(params)
我知道 Iterable 是不正确的，因为 mypy 告诉我：
error: Argument 1 to "join" of "str" has incompatible type Tuple[Iterable[Any], ...]; expected Iterable[str]
……但是我不明白为什么。
当注解与 *args 风格的参数列表结合使用时，注解指定了每个预期参数的类型。如PEP 484所述：
Arbitrary argument lists can as well be type annotated, so that the
definition:
def foo(*args: str, **kwds: int): ...
is acceptable and it means that, e.g., all of the following represent
function calls with valid types of arguments:
foo('a', 'b', 'c')
foo(x=1, y=2)
foo('', z=0)
In the body of function foo, the type of variable args is deduced as
Tuple[str, ...] and the type of variable kwds is Dict[str, int].
在你的例子中，由于 params 应该是一个字符串元组，正确的注释是 str:
def f(*params: str) -> str:
return ":".join(params)
我不知道如何正确注释这段代码：
from typing import Iterable
def f(*params: Iterable) -> str:
return ":".join(params)
我知道 Iterable 是不正确的，因为 mypy 告诉我：
error: Argument 1 to "join" of "str" has incompatible type Tuple[Iterable[Any], ...]; expected Iterable[str]
……但是我不明白为什么。
当注解与 *args 风格的参数列表结合使用时，注解指定了每个预期参数的类型。如PEP 484所述：
Arbitrary argument lists can as well be type annotated, so that the definition:
def foo(*args: str, **kwds: int): ...is acceptable and it means that, e.g., all of the following represent function calls with valid types of arguments:
foo('a', 'b', 'c') foo(x=1, y=2) foo('', z=0)In the body of function
foo, the type of variableargsis deduced asTuple[str, ...]and the type of variablekwdsisDict[str, int].
在你的例子中，由于 params 应该是一个字符串元组，正确的注释是 str:
def f(*params: str) -> str:
return ":".join(params)