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ruff/crates/ty_python_semantic/resources/mdtest/subscript/tuple.md

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Tuple subscripts

Indexing

t = (1, "a", "b")

reveal_type(t[0])  # revealed: Literal[1]
reveal_type(t[1])  # revealed: Literal["a"]
reveal_type(t[-1])  # revealed: Literal["b"]
reveal_type(t[-2])  # revealed: Literal["a"]

reveal_type(t[False])  # revealed: Literal[1]
reveal_type(t[True])  # revealed: Literal["a"]

a = t[4]  # error: [index-out-of-bounds]
reveal_type(a)  # revealed: Unknown

b = t[-4]  # error: [index-out-of-bounds]
reveal_type(b)  # revealed: Unknown

Slices

def _(m: int, n: int):
    t = (1, "a", None, b"b")

    reveal_type(t[0:0])  # revealed: tuple[()]
    reveal_type(t[0:1])  # revealed: tuple[Literal[1]]
    reveal_type(t[0:2])  # revealed: tuple[Literal[1], Literal["a"]]
    reveal_type(t[0:4])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]
    reveal_type(t[0:5])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]
    reveal_type(t[1:3])  # revealed: tuple[Literal["a"], None]

    reveal_type(t[-2:4])  # revealed: tuple[None, Literal[b"b"]]
    reveal_type(t[-3:-1])  # revealed: tuple[Literal["a"], None]
    reveal_type(t[-10:10])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]

    reveal_type(t[0:])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]
    reveal_type(t[2:])  # revealed: tuple[None, Literal[b"b"]]
    reveal_type(t[4:])  # revealed: tuple[()]
    reveal_type(t[:0])  # revealed: tuple[()]
    reveal_type(t[:2])  # revealed: tuple[Literal[1], Literal["a"]]
    reveal_type(t[:10])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]
    reveal_type(t[:])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]

    reveal_type(t[::-1])  # revealed: tuple[Literal[b"b"], None, Literal["a"], Literal[1]]
    reveal_type(t[::2])  # revealed: tuple[Literal[1], None]
    reveal_type(t[-2:-5:-1])  # revealed: tuple[None, Literal["a"], Literal[1]]
    reveal_type(t[::-2])  # revealed: tuple[Literal[b"b"], Literal["a"]]
    reveal_type(t[-1::-3])  # revealed: tuple[Literal[b"b"], Literal[1]]

    reveal_type(t[None:2:None])  # revealed: tuple[Literal[1], Literal["a"]]
    reveal_type(t[1:None:1])  # revealed: tuple[Literal["a"], None, Literal[b"b"]]
    reveal_type(t[None:None:None])  # revealed: tuple[Literal[1], Literal["a"], None, Literal[b"b"]]

    start = 1
    stop = None
    step = 2
    reveal_type(t[start:stop:step])  # revealed: tuple[Literal["a"], Literal[b"b"]]

    reveal_type(t[False:True])  # revealed: tuple[Literal[1]]
    reveal_type(t[True:3])  # revealed: tuple[Literal["a"], None]

    t[0:4:0]  # error: [zero-stepsize-in-slice]
    t[:4:0]  # error: [zero-stepsize-in-slice]
    t[0::0]  # error: [zero-stepsize-in-slice]
    t[::0]  # error: [zero-stepsize-in-slice]

    tuple_slice = t[m:n]
    # TODO: Should be `tuple[Literal[1, 'a', b"b"] | None, ...]`
    reveal_type(tuple_slice)  # revealed: tuple[Unknown, ...]

Inheritance

[environment]
python-version = "3.9"

class A(tuple[int, str]): ...

# revealed: tuple[<class 'A'>, <class 'tuple[@Todo(Generic tuple specializations), ...]'>, <class 'Sequence[@Todo(Generic tuple specializations)]'>, <class 'Reversible[@Todo(Generic tuple specializations)]'>, <class 'Collection[@Todo(Generic tuple specializations)]'>, <class 'Iterable[@Todo(Generic tuple specializations)]'>, <class 'Container[@Todo(Generic tuple specializations)]'>, typing.Protocol[_T_co], typing.Generic[_T_co], <class 'object'>]
reveal_type(A.__mro__)

typing.Tuple

Correspondence with tuple

typing.Tuple can be used interchangeably with tuple:

from typing import Any, Tuple

class A: ...

def _(c: Tuple, d: Tuple[int, A], e: Tuple[Any, ...]):
    reveal_type(c)  # revealed: tuple[Unknown, ...]
    reveal_type(d)  # revealed: tuple[int, A]
    reveal_type(e)  # revealed: tuple[Any, ...]

Inheritance

Inheriting from Tuple results in a MRO with builtins.tuple and typing.Generic. Tuple itself is not a class.

from typing import Tuple

class C(Tuple): ...

# revealed: tuple[<class 'C'>, <class 'tuple[Unknown, ...]'>, <class 'Sequence[Unknown]'>, <class 'Reversible[Unknown]'>, <class 'Collection[Unknown]'>, <class 'Iterable[Unknown]'>, <class 'Container[Unknown]'>, typing.Protocol[_T_co], typing.Generic[_T_co], <class 'object'>]
reveal_type(C.__mro__)