For instance, what is a good syntax for a type like that:
list[int | list[int | ...]]
Basically, for a list of ints that could be of any (strictly positive) dimension.
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LoneCodeRanger
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Maybe something like that would make sense: `T_ = Grid[Node | T_]`... But this does not seem to be a proper syntax. – LoneCodeRanger Sep 27 '22 at 22:48
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1Recursive types are not yet officially supported, but see https://github.com/python/mypy/pull/13297. – chepner Sep 27 '22 at 22:49
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1The *syntax* is fine; it's the semantics that fall apart. (Python would accept `T_ = Grid[Node | 'T_']`--a standard forward reference--but `mypy` will fail to resolve the cycle.) – chepner Sep 27 '22 at 22:50
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@chepner I think `pyright` supports recursive definitions – juanpa.arrivillaga Sep 27 '22 at 22:54
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1related: https://stackoverflow.com/questions/53845024/defining-a-recursive-type-hint-in-python – juanpa.arrivillaga Sep 27 '22 at 22:57
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I was able to find a solution, by following the logic in this answer (as suggested by @juanpa.arrivillaga), and using a forward reference.
The type (T) for an n-dimensional list of ints could be noted as:
import typing
T = list[typing.Union[int, 'T']]
N.B.: whereas typing.Union(T1, T2) can also be written as T1 | T2, it doesn't work in the context of this answer (as of Python 3.9):
>>> T = list[int | 'T']
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'str'
LoneCodeRanger
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