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typing_extensions — Backported typing features

Version: 4.15.0 Type: Pure Python (single file: typing_extensions.py) SPM target: Typing_extensions Auto-included by: Pydantic, attrs, referencing, narwhals, FastAPI, SQLModel, and ~every typed library that wants to support multiple Python versions Total Python modules: 1 (a ~4300-line single file)

The forward-compat shim for typing. Any feature added to stdlib typing in a recent Python version is re-implemented here so libraries can use it on older runtimes (and import it conditionally with if sys.version_info < (3, X): from typing_extensions import ...).

On iOS we ship Python 3.14, so many of these symbols just delegate to stdlib typing, but downstream code still needs typing_extensions for the names that haven't graduated yet (TypeIs, Doc, ReadOnly, the new TypeVar with default=, etc.).

Module

Single file at app_packages/site-packages/typing_extensions.py (~4317 lines).

Categories of what it provides

Category Symbols
Backported / re-exported typing primitives Any, ClassVar, Concatenate, Final, LiteralString, ParamSpec, ParamSpecArgs, ParamSpecKwargs, Self, Type, TypeAlias, TypeAliasType, TypeGuard, TypeIs, TypeVar, TypeVarTuple, Unpack
ABCs Awaitable, AsyncIterator, AsyncIterable, Coroutine, AsyncGenerator, AsyncContextManager, Buffer, ChainMap, ContextManager, Counter, Deque, DefaultDict, OrderedDict
Concrete collections / Protocol Protocol, runtime_checkable, Generic, NamedTuple, TypedDict, Required, NotRequired, ReadOnly, NoExtraItems, Sentinel
Decorators / helpers final, overload, override, deprecated, assert_type, assert_never, clear_overloads, get_overloads, get_args, get_origin, get_type_hints, get_protocol_members, is_protocol, is_typeddict, reveal_type
PEP 727 / new (4.x) Doc, evaluate_forward_ref, Format, Sentinel, get_annotations, get_evaluate_type_params, NamedTuple (extended)
Newer Python 3.13 / 3.14 backports CapsuleType, TypeAliasType with generics, TypeVar(default=...), ParamSpec(default=...), TypeVarTuple(default=...), Never, NoReturn, Self, Required, NotRequired, LiteralString, Literal extensions

If you want the full export list:

import typing_extensions
print(sorted(typing_extensions.__all__))

(~180 symbols.)

iOS-specific patches

None. typing_extensions is pure Python with no platform branches — it only branches on sys.version_info. On Python 3.14 (what iOS ships), almost everything delegates to stdlib typing; new symbols that haven't been upstreamed yet are implemented locally.

Standalone example

from typing_extensions import (
    TypeVar, Self, override, deprecated, Doc, Annotated, NotRequired, TypedDict,
)

T = TypeVar("T", default=int)   # Python 3.13+ feature, available here

class Stack(list[T]):
    def push(self, value: T) -> Self:
        self.append(value)
        return self            # Self lets the return type stay precise in subclasses

    @override
    def __repr__(self) -> str:
        return f"Stack({list.__repr__(self)})"

class Profile(TypedDict):
    name: str
    bio: NotRequired[str]                                          # optional key
    age: Annotated[int, Doc("Age in years; non-negative")]         # PEP 727 doc string

@deprecated("Use Stack.push instead")
def push_legacy(s, v):
    s.push(v)

See also