Metadata-Version: 2.1
Name: typing_extensions
Version: 4.4.0
Summary: Backported and Experimental Type Hints for Python 3.7+
Keywords: annotations,backport,checker,checking,function,hinting,hints,type,typechecking,typehinting,typehints,typing
Author-email: "Guido van Rossum, Jukka Lehtosalo, Łukasz Langa, Michael Lee" <levkivskyi@gmail.com>
Requires-Python: >=3.7
Description-Content-Type: text/markdown
Classifier: Development Status :: 5 - Production/Stable
Classifier: Environment :: Console
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Python Software Foundation License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: Python :: 3.7
Classifier: Programming Language :: Python :: 3.8
Classifier: Programming Language :: Python :: 3.9
Classifier: Programming Language :: Python :: 3.10
Classifier: Topic :: Software Development
Project-URL: Bug Tracker, https://github.com/python/typing_extensions/issues
Project-URL: Changes, https://github.com/python/typing_extensions/blob/main/CHANGELOG.md
Project-URL: Documentation, https://typing.readthedocs.io/
Project-URL: Home, https://github.com/python/typing_extensions
Project-URL: Q & A, https://github.com/python/typing/discussions
Project-URL: Repository, https://github.com/python/typing_extensions

# Typing Extensions

[![Chat at https://gitter.im/python/typing](https://badges.gitter.im/python/typing.svg)](https://gitter.im/python/typing)

## Overview

The `typing_extensions` module serves two related purposes:

- Enable use of new type system features on older Python versions. For example,
  `typing.TypeGuard` is new in Python 3.10, but `typing_extensions` allows
  users on previous Python versions to use it too.
- Enable experimentation with new type system PEPs before they are accepted and
  added to the `typing` module.

New features may be added to `typing_extensions` as soon as they are specified
in a PEP that has been added to the [python/peps](https://github.com/python/peps)
repository. If the PEP is accepted, the feature will then be added to `typing`
for the next CPython release. No typing PEP has been rejected so far, so we
haven't yet figured out how to deal with that possibility.

Starting with version 4.0.0, `typing_extensions` uses
[Semantic Versioning](https://semver.org/). The
major version is incremented for all backwards-incompatible changes.
Therefore, it's safe to depend
on `typing_extensions` like this: `typing_extensions >=x.y, <(x+1)`,
where `x.y` is the first version that includes all features you need.

`typing_extensions` supports Python versions 3.7 and higher. In the future,
support for older Python versions will be dropped some time after that version
reaches end of life.

## Included items

This module currently contains the following:

- Experimental features

  - `override` (see PEP 698)
  - The `default=` argument to `TypeVar`, `ParamSpec`, and `TypeVarTuple` (see PEP 696)
  - The `infer_variance=` argument to `TypeVar` (see PEP 695)

- In `typing` since Python 3.11

  - `assert_never`
  - `assert_type`
  - `clear_overloads`
  - `@dataclass_transform()` (see PEP 681)
  - `get_overloads`
  - `LiteralString` (see PEP 675)
  - `Never`
  - `NotRequired` (see PEP 655)
  - `reveal_type`
  - `Required` (see PEP 655)
  - `Self` (see PEP 673)
  - `TypeVarTuple` (see PEP 646; the `typing_extensions` version supports the `default=` argument from PEP 696)
  - `Unpack` (see PEP 646)

- In `typing` since Python 3.10

  - `Concatenate` (see PEP 612)
  - `ParamSpec` (see PEP 612; the `typing_extensions` version supports the `default=` argument from PEP 696)
  - `ParamSpecArgs` (see PEP 612)
  - `ParamSpecKwargs` (see PEP 612)
  - `TypeAlias` (see PEP 613)
  - `TypeGuard` (see PEP 647)
  - `is_typeddict`

- In `typing` since Python 3.9

  - `Annotated` (see PEP 593)

- In `typing` since Python 3.8

  - `final` (see PEP 591)
  - `Final` (see PEP 591)
  - `Literal` (see PEP 586)
  - `Protocol` (see PEP 544)
  - `runtime_checkable` (see PEP 544)
  - `TypedDict` (see PEP 589)
  - `get_origin` (`typing_extensions` provides this function only in Python 3.7+)
  - `get_args` (`typing_extensions` provides this function only in Python 3.7+)

- In `typing` since Python 3.7

  - `OrderedDict`

- In `typing` since Python 3.5 or 3.6 (see [the typing documentation](https://docs.python.org/3.10/library/typing.html) for details)

  - `AsyncContextManager`
  - `AsyncGenerator`
  - `AsyncIterable`
  - `AsyncIterator`
  - `Awaitable`
  - `ChainMap`
  - `ClassVar` (see PEP 526)
  - `ContextManager`
  - `Coroutine`
  - `Counter`
  - `DefaultDict`
  - `Deque`
  - `NewType`
  - `NoReturn`
  - `overload`
  - `Text`
  - `Type`
  - `TYPE_CHECKING`
  - `get_type_hints`

- The following have always been present in `typing`, but the `typing_extensions` versions provide
  additional features:

  - `Any` (supports inheritance since Python 3.11)
  - `NamedTuple` (supports multiple inheritance with `Generic` since Python 3.11)
  - `TypeVar` (see PEPs 695 and 696)

# Other Notes and Limitations

Certain objects were changed after they were added to `typing`, and
`typing_extensions` provides a backport even on newer Python versions:

- `TypedDict` does not store runtime information
  about which (if any) keys are non-required in Python 3.8, and does not
  honor the `total` keyword with old-style `TypedDict()` in Python
  3.9.0 and 3.9.1. `TypedDict` also does not support multiple inheritance
  with `typing.Generic` on Python <3.11.
- `get_origin` and `get_args` lack support for `Annotated` in
  Python 3.8 and lack support for `ParamSpecArgs` and `ParamSpecKwargs`
  in 3.9.
- `@final` was changed in Python 3.11 to set the `.__final__` attribute.
- `@overload` was changed in Python 3.11 to make function overloads
  introspectable at runtime. In order to access overloads with
  `typing_extensions.get_overloads()`, you must use
  `@typing_extensions.overload`.
- `NamedTuple` was changed in Python 3.11 to allow for multiple inheritance
  with `typing.Generic`.
- Since Python 3.11, it has been possible to inherit from `Any` at
  runtime. `typing_extensions.Any` also provides this capability.
- `TypeVar` gains two additional parameters, `default=` and `infer_variance=`,
  in the draft PEPs 695 and 696, which are being considered for inclusion
  in Python 3.12.

There are a few types whose interface was modified between different
versions of typing. For example, `typing.Sequence` was modified to
subclass `typing.Reversible` as of Python 3.5.3.

These changes are _not_ backported to prevent subtle compatibility
issues when mixing the differing implementations of modified classes.

Certain types have incorrect runtime behavior due to limitations of older
versions of the typing module:

- `ParamSpec` and `Concatenate` will not work with `get_args` and
  `get_origin`. Certain PEP 612 special cases in user-defined
  `Generic`s are also not available.

These types are only guaranteed to work for static type checking.

## Running tests

To run tests, navigate into the appropriate source directory and run
`test_typing_extensions.py`.

