CODEWITHSUNDEEP
pythonpython-typing
mutableVoid
mutableVoid

Reputation: 1526

TypeVarTuple Unpack all contained types and use them as type arguments

I would like to use a generic class in Python that is instantiated with a variable number of type parameters. This can be achieved using TypeVarTuple. For each of these type parameters, I want to fill a data structure (e.g., a list). The list can have a different length for each data type. Ideally, I would like to type hint a tuple of lists, each corresponding to a type from the TypeVarTuple.

Here is a very simplified example of what I would like to achieve (note that the syntax below does not work):

from typing import Generic, Tuple, List
from typing_extensions import TypeVarTuple, Unpack

Ts = TypeVarTuple('Ts')

class Test(Generic[Unpack[Ts]]):
    def __init__(self) -> None:
        self.content: Unpack[Tuple[List[Ts]]] = []

    def call(self, *values: Unpack[List[Ts]]):
        for v, c in zip(values, self.content):
            c.extend(v)  # noqa

class Implementation(Test[int, str, int]):
    pass

i = Implementation()
i.call([1, 2, 3], [], [2])

Is something like this possible with Python's type hinting? If so, how can it be properly implemented?

Upvotes: 0

Views: 379

Answers (1)

Boštjan Mejak
Boštjan Mejak

Reputation: 997

Use *-unpacking, so like class Test(Generic[*Ts]): ...

Since Ts is a TypeVarTuple, using *Ts is valid in this context and also exactly what you were looking for.

Upvotes: 0

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