Class TypedDictType

mypy/types.py:2926–3103

Type of TypedDict object {'k1': v1, ..., 'kn': vn}. A TypedDict object is a dictionary with specific string (literal) keys. Each key has a value with a distinct type that depends on the key. TypedDict objects are normal dict objects at runtime. A TypedDictType can be either named o

class TypedDictType(ProperType):
    """Type of TypedDict object {'k1': v1, ..., 'kn': vn}.

    A TypedDict object is a dictionary with specific string (literal) keys. Each
    key has a value with a distinct type that depends on the key. TypedDict objects
    are normal dict objects at runtime.

    A TypedDictType can be either named or anonymous. If it's anonymous, its
    fallback will be typing_extensions._TypedDict (Instance). _TypedDict is a subclass
    of Mapping[str, object] and defines all non-mapping dict methods that TypedDict
    supports. Some dict methods are unsafe and not supported. _TypedDict isn't defined
    at runtime.

    If a TypedDict is named, its fallback will be an Instance of the named type
    (ex: "Point") whose TypeInfo has a typeddict_type that is anonymous. This
    is similar to how named tuples work.

    TODO: The fallback structure is perhaps overly complicated.
    """

    __slots__ = (
        "items",
        "required_keys",
        "readonly_keys",
        "fallback",
        "extra_items_from",
        "to_be_mutated",
    )

    items: dict[str, Type]  # item_name -> item_type
    required_keys: set[str]
    readonly_keys: set[str]
    fallback: Instance

    extra_items_from: list[ProperType]  # only used during semantic analysis
    to_be_mutated: bool  # only used in a plugin for `.update`, `|=`, etc

    def __init__(
        self,
        items: dict[str, Type],
        required_keys: set[str],
        readonly_keys: set[str],
        fallback: Instance,
        line: int = -1,
        column: int = -1,
    ) -> None:
        super().__init__(line, column)
        self.items = items
        self.required_keys = required_keys
        self.readonly_keys = readonly_keys
        self.fallback = fallback
        self.can_be_true = len(self.items) > 0
        self.can_be_false = len(self.required_keys) == 0
        self.extra_items_from = []
        self.to_be_mutated = False

    def accept(self, visitor: TypeVisitor[T]) -> T:
        return visitor.visit_typeddict_type(self)