Reveal_type(test(*)) # note: Revealed type is 'builtins. Reveal_type(test(*(1, 2,))) # note: Revealed type is 'Tuple' It is worth noting that while packing into variadic parameters can be typed, unpacking arguments generally cannot: Any container but tuple is arbitrary length – for example List = – and thus has no exact type information for its elements. We can use the iterable unpacking operator when defining sequences to unpack the elements of a subsequence (or iterable) into the final sequence. Reveal_type(test(1, 2, 3, 4)) # note: Revealed type is 'builtins.tuple' Reveal_type(test(1, 2, "three", 4)) # note: Revealed type is 'builtins.tuple' Reveal_type(test(1, 2, "three")) # note: Revealed type is 'Tuple' # implementation can use Any to simplify matching all overloads # catch all variadic signature for all other test(*args: T) -> Tuple. # positional parameters via double underscore test(_arg1: T1, _arg2: T2) -> Tuple: test(_arg1: T1, _arg2: T2, _arg3: T3) -> Tuple. # positional parameters via `, /` – Python 3.8+ test(arg1: T1, /) -> Tuple. from typing import TypeVar, Tuple, Any, overload A final catch-all variadic handles the case of more arguments. The correct approach to annotate *args is to decide on some level of supported "variance length", and explicitly type this using Notably, explicit parameters must be positional only – they must be either _anonymous or positional, /. Note that older versions may not support the *TS syntax and need typing.Unpack instead, which is also available via typing_extensions. Īrgs_to_tuple(1, 'a') # Inferred type is Tuple Unpacking a sequence into separate variables is a simple task if you use Python for it as well. If *args is annotated as a type variable tuple, however, the types of the individual arguments become the types in the type variable tuple: Ts = TypeVarTuple('Ts')ĭef args_to_tuple(*args: *Ts) -> Tuple. python variable datastructure unpack We all know pretty much that Python provides a variety of well known built-in data structures, including lists, sets and so on. PEP 646 - Variadic Generics will enable annotating variadics in Python 3.11 or via typing_extensions. TLDR: is currently the only viable way to annotate some level of variance.
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