英文:
Typehint method as returning return type of other method in python?
问题
I have a base class:
from abc import abstractmethodclass Thing:@abstractmethoddef _process(self):...def process(self, x: int):self.pre_process(x)return self._process()
How do I typehint process as returning the return type of _process? My first thought was something like:
from abc import abstractmethodfrom typing import TypeVarclass Thing:T = TypeVar("T")@abstractmethoddef _process(self) -> T:...def process(self, x: int) -> T:...
But mypy 1.3.0 complains quite rightly that T is only present once in the function signature:
> mypy /tmp/t.py...error: A function returning TypeVar should receive at least one argument containing the same TypeVar...
英文:
I have a base class:
from abc import abstractmethodclass Thing:@abstractmethoddef _process(self):...def process(self, x: int):self.pre_process(x)return self._process()
How do I typehint process as returning the return type of _process? My first thought was something like:
from abc import abstractmethodfrom typing import TypeVarclass Thing:T = TypeVar("T")@abstractmethoddef _process(self) -> T:...def process(self, x: int) -> T:...
But mypy 1.3.0 complains quite rightly that T is only present once in the function signature:
> mypy /tmp/t.py...error: A function returning TypeVar should receive at least one argument containing the same TypeVar...
答案1
得分: 3
You can make Thing inherit Generic[T].
from typing import TypeVarfrom typing import Genericfrom abc import abstractmethodT = TypeVar("T")class Thing(Generic[T]):@abstractmethoddef _process(self) -> T:...def process(self, x: int) -> T:return self._process()
> mypy /tmp/t.pySuccess: no issues found in 1 source file
Now you can inherit from Thing like this:
class A(Thing[list]):def _process(self) -> list:return []
英文:
You can make Thing inherit Generic[T].
from typing import TypeVarfrom typing import Genericfrom abc import abstractmethodT = TypeVar("T")class Thing(Generic[T]):@abstractmethoddef _process(self) -> T:...def process(self, x: int) -> T:return self._process()
> mypy /tmp/t.pySuccess: no issues found in 1 source file
Now you can inherit from Thing like this:
class A(Thing[list]):def _process(self) -> list:return []
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