我有一个字典,它使用两种不同类型的键(
city
和village
)来跟踪两种不同类型的值(比如说city_key
和village_key
)。我想用泛型注释这个字典,这样当字典接收到 city_key
类型的键时 mypy/Pyright 应该将返回值注释为 city
。同样,如果您尝试将 city
值分配给 village_key
,mypy/pyright 应该会抛出错误。
另一种方法是维护两本不同的字典,一本用于城市,一本用于村庄,但我很好奇是否可以只用一本字典。
有一个和我一样的问题这里,但没有得到解答。
一些伪代码来展示我在实践中的目标:
# two types of aliased keys
# ... edited to use NewType as per juanpa.arrivillaga comment
CityKey = NewType("CityKey", str)
VillageKey = NewType("VillageKey", str)
# two types of values, city and village
class City:...
class Village:...
# key generator that returns city or village key based on type of input
def generate_key(settlement: City | Village) -> CityKey | VillageKey: ...
# declare some keys & values
london = City("London")
london_key = generate_key(london)
mousehole = Village("Mousehole")
mousehole_key = generate_key(village)
# instantiate the dictionary
data: [????] = {}
# assign city to city key, and village to village key
data[london_key] = london
data[mousehole_key] = mousehole
# trying to assign village to city key should raise a type check error
data[london_key] = mousehole
# type of value accessed by village key should be village
reveal_type(data[mousehole_key]) # Type[Village]
您可以使用
typing.overload
来实现此目的,这可以帮助我们从 Callable[[A1 | B1], A2 | B2]
等类型转变为可以是 Callable[[A1], A2]
或 Callable[[B1], B2]
的类型,以及 dict
的子类。
from typing import overload
@overload
def generate_key(settlement: City) -> CityKey:
# Just a stub
...
@overload
def generate_key(settlement: Village) -> VillageKey:
# Just a stub
...
def generate_key(settlement):
# Contains the actual implementation
[...]
class CityOrVillageDict(dict):
@overload
def __setitem__(self, key: CityKey, value: City) -> None:
# Just a stub
...
@overload
def __setitem__(self, key: VillageKey, value: Village) -> None:
# Just a stub
...
def __setitem__(self, key, value):
# Overloaded functions need an implementation
super().__setitem__(key, value)
@overload
def __getitem__(self, key: CityKey) -> City:
# Just a stub
...
@overload
def __getitem__(self, key: VillageKey) -> Village:
# Just a stub
...
def __getitem__(self, key):
# Overloaded functions need an implementation
return super().__getitem__(key)
data = CityOrVillageDict()