Class TupleType

mypy/types.py:2750–2923

The tuple type Tuple[T1, ..., Tn] (at least one type argument). Instance variables: items: Tuple item types partial_fallback: The (imprecise) underlying instance type that is used for non-tuple methods. This is generally builtins.tuple[Any, ...] for regul

class TupleType(ProperType):
    """The tuple type Tuple[T1, ..., Tn] (at least one type argument).

    Instance variables:
        items: Tuple item types
        partial_fallback: The (imprecise) underlying instance type that is used
            for non-tuple methods. This is generally builtins.tuple[Any, ...] for
            regular tuples, but it's different for named tuples and classes with
            a tuple base class. Use mypy.typeops.tuple_fallback to calculate the
            precise fallback type derived from item types.
        implicit: If True, derived from a tuple expression (t,....) instead of Tuple[t, ...]
    """

    __slots__ = ("items", "partial_fallback", "implicit")

    items: list[Type]
    partial_fallback: Instance
    implicit: bool

    def __init__(
        self,
        items: list[Type],
        fallback: Instance,
        line: int = -1,
        column: int = -1,
        implicit: bool = False,
    ) -> None:
        super().__init__(line, column)
        self.partial_fallback = fallback
        self.items = items
        self.implicit = implicit

    def can_be_true_default(self) -> bool:
        if self.can_be_any_bool():
            # Corner case: it is a `NamedTuple` with `__bool__` method defined.
            # It can be anything: both `True` and `False`.
            return True
        return self.length() > 0

    def can_be_false_default(self) -> bool:
        if self.can_be_any_bool():
            # Corner case: it is a `NamedTuple` with `__bool__` method defined.
            # It can be anything: both `True` and `False`.
            return True
        if self.length() == 0:
            return True
        if self.length() > 1:
            return False
        # Special case tuple[*Ts] may or may not be false.
        item = self.items[0]
        if not isinstance(item, UnpackType):
            return False
        if not isinstance(item.type, TypeVarTupleType):
            # Non-normalized tuple[int, ...] can be false.
            return True
        return item.type.min_len == 0

    def can_be_any_bool(self) -> bool: