How do I specify this kind of variable argument tuple with python typing?

Question

I'm trying to do this, but I'm not sure how to specify the type signature:

def initialize_signals(
        self,
        command: InitializeCommand,
        initializers: Iterable[Union[
            Tuple[SignalNode],
            Tuple[SignalNode, Any, ...]
                  ]]):
    for x, *args in initializers:
        potential_update = command.create_potential_update(x, *args)

anthony sottile · Accepted Answer · 2019-02-24 20:39:39Z

6

there currently isn't an annotation which can represent the addition of a fixed-length tuple with a variable length tuple.

here's some code I used to determine how mypy's inference would handle something like this:

from typing import Tuple

x: Tuple[int, ...]
y = ('hi', *x)
z = (*x,)
reveal_type(y)
reveal_type(z)

and output:

$ mypy t.py
t.py:6: error: Revealed type is 'builtins.tuple[builtins.object*]'
t.py:7: error: Revealed type is 'builtins.tuple[builtins.int*]'

despite knowing that it's a variable-length int tuple it decays to object.

You may want to refactor your code to use Tuple[SignalNode, Tuple[Any, ...]] instead

answered Feb 24, 2019 at 20:39

anthony sottile

72.1k19 gold badges199 silver badges248 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Neil G Over a year ago

Thanks! I know that the refactoring you suggest is more logical. However, this code is called so much that it feels painful to add (,) all over the place. It does seem that this feature could theoretically (and without breaking anything) be added to python typing.

Collectives™ on Stack Overflow

How do I specify this kind of variable argument tuple with python typing?

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related