We’ve just uploaded mypy 1.14 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
Mypy is a static type checker for Python. This release includes new features and bug fixes.
You can install it as follows:
python3 -m pip install -U mypy
You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).
Change to Enum Membership Semantics
As per the updated [typing specification for enums](https://typing.readthedocs.io/en/latest/spec/enums.html#defining-members),
enum members must be left unannotated.
python
class Pet(Enum):
CAT = 1 Member attribute
DOG = 2 Member attribute
New error: Enum members must be left unannotated
WOLF: int = 3
species: str Considered a non-member attribute
In particular, the specification change can result in issues in type stubs (`.pyi` files), since
historically it was common to leave the value absent:
python
In a type stub (.pyi file)
class Pet(Enum):
Change in semantics: previously considered members,
now non-member attributes
CAT: int
DOG: int
Mypy will now issue a warning if it detects this
situation in type stubs:
> Detected enum "Pet" in a type stub with zero
> members. There is a chance this is due to a recent
> change in the semantics of enum membership. If so,
> use `member = value` to mark an enum member,
> instead of `member: type`
class Pet(Enum):
As per the specification, you should now do one of
the following:
DOG = 1 Member attribute with value 1 and known type
WOLF = cast(int, ...) Member attribute with unknown
value but known type
LION = ... Member attribute with unknown value and
unknown type
Contributed by Terence Honles (PR [17207](https://github.com/python/mypy/pull/17207)) and
Shantanu Jain (PR [18068](https://github.com/python/mypy/pull/18068)).
Support for deprecated Decorator (PEP 702)
Mypy can now issue errors or notes when code imports a deprecated feature
explicitly with a `from mod import depr` statement, or uses a deprecated feature
imported otherwise or defined locally. Features are considered deprecated when
decorated with `warnings.deprecated`, as specified in [PEP 702](https://peps.python.org/pep-0702).
You can enable the error code via `--enable-error-code=deprecated` on the mypy
command line or `enable_error_code = deprecated` in the mypy config file.
Use the command line flag `--report-deprecated-as-note` or config file option
`report_deprecated_as_note=True` to turn all such errors into notes.
Deprecation errors will be enabled by default in a future mypy version.
This feature was contributed by Christoph Tyralla.
List of changes:
* Add basic support for PEP 702 (`deprecated`) (Christoph Tyralla, PR [17476](https://github.com/python/mypy/pull/17476))
* Support descriptors with `deprecated` (Christoph Tyralla, PR [18090](https://github.com/python/mypy/pull/18090))
* Make "deprecated" note an error, disabled by default (Valentin Stanciu, PR [18192](https://github.com/python/mypy/pull/18192))
* Consider all possible type positions with `deprecated` (Christoph Tyralla, PR [17926](https://github.com/python/mypy/pull/17926))
* Improve the handling of explicit type annotations in assignment statements with `deprecated` (Christoph Tyralla, PR [17899](https://github.com/python/mypy/pull/17899))
Optionally Analyzing Untyped Modules
Mypy normally doesn't analyze imports from third-party modules (installed using pip, for example)
if there are no stubs or a py.typed marker file. To force mypy to analyze these imports, you
can now use the `--follow-untyped-imports` flag or set the `follow_untyped_imports`
config file option to True. This can be set either in the global section of your mypy config
file, or individually on a per-module basis.
This feature was contributed by Jannick Kremer.
List of changes:
* Implement flag to allow type checking of untyped modules (Jannick Kremer, PR [17712](https://github.com/python/mypy/pull/17712))
* Warn about `--follow-untyped-imports` (Shantanu, PR [18249](https://github.com/python/mypy/pull/18249))
Support New Style Type Variable Defaults (PEP 696)
Mypy now supports type variable defaults using the new syntax described in PEP 696, which
was introduced in Python 3.13. Example:
python
dataclass
class Box[T = int]: Set default for "T"
value: T | None = None
reveal_type(Box()) type is Box[int], since it's the default
reveal_type(Box(value="Hello World!")) type is Box[str]
This feature was contributed by Marc Mueller (PR [17985](https://github.com/python/mypy/pull/17985)).
Improved For Loop Index Variable Type Narrowing
Mypy now preserves the literal type of for loop index variables, to support `TypedDict`
lookups. Example:
python
from typing import TypedDict
class X(TypedDict):
hourly: int
daily: int
def func(x: X) -> int:
s = 0
for var in ("hourly", "daily"):
"Union[Literal['hourly']?, Literal['daily']?]"
reveal_type(var)
x[var] no longer triggers a literal-required error
s += x[var]
return s
This was contributed by Marc Mueller (PR [18014](https://github.com/python/mypy/pull/18014)).
Mypyc Improvements
* Document optimized bytes operations and additional str operations (Jukka Lehtosalo, PR [18242](https://github.com/python/mypy/pull/18242))
* Add primitives and specialization for `ord()` (Jukka Lehtosalo, PR [18240](https://github.com/python/mypy/pull/18240))
* Optimize `str.encode` with specializations for common used encodings (Valentin Stanciu, PR [18232](https://github.com/python/mypy/pull/18232))
* Fix fall back to generic operation for staticmethod and classmethod (Advait Dixit, PR [18228](https://github.com/python/mypy/pull/18228))
* Support unicode surrogates in string literals (Jukka Lehtosalo, PR [18209](https://github.com/python/mypy/pull/18209))
* Fix index variable in for loop with `builtins.enumerate` (Advait Dixit, PR [18202](https://github.com/python/mypy/pull/18202))
* Fix check for enum classes (Advait Dixit, PR [18178](https://github.com/python/mypy/pull/18178))
* Fix loading type from imported modules (Advait Dixit, PR [18158](https://github.com/python/mypy/pull/18158))
* Fix initializers of final attributes in class body (Jared Hance, PR [18031](https://github.com/python/mypy/pull/18031))
* Fix name generation for modules with similar full names (aatle, PR [18001](https://github.com/python/mypy/pull/18001))
* Fix relative imports in `__init__.py` (Shantanu, PR [17979](https://github.com/python/mypy/pull/17979))
* Optimize dunder methods (jairov4, PR [17934](https://github.com/python/mypy/pull/17934))
* Replace deprecated `_PyDict_GetItemStringWithError` (Marc Mueller, PR [17930](https://github.com/python/mypy/pull/17930))
* Fix wheel build for cp313-win (Marc Mueller, PR [17941](https://github.com/python/mypy/pull/17941))
* Use public PyGen_GetCode instead of vendored implementation (Marc Mueller, PR [17931](https://github.com/python/mypy/pull/17931))
* Optimize calls to final classes (jairov4, PR [17886](https://github.com/python/mypy/pull/17886))
* Support ellipsis (`...`) expressions in class bodies (Newbyte, PR [17923](https://github.com/python/mypy/pull/17923))
* Sync `pythoncapi_compat.h` (Marc Mueller, PR [17929](https://github.com/python/mypy/pull/17929))
* Add `runtests.py mypyc-fast` for running fast mypyc tests (Jukka Lehtosalo, PR [17906](https://github.com/python/mypy/pull/17906))
Stubgen Improvements
* Do not include mypy generated symbols (Ali Hamdan, PR [18137](https://github.com/python/mypy/pull/18137))
* Fix `FunctionContext.fullname` for nested classes (Chad Dombrova, PR [17963](https://github.com/python/mypy/pull/17963))
* Add flagfile support (Ruslan Sayfutdinov, PR [18061](https://github.com/python/mypy/pull/18061))
* Add support for PEP 695 and PEP 696 syntax (Ali Hamdan, PR [18054](https://github.com/python/mypy/pull/18054))
Stubtest Improvements
* Allow the use of `--show-traceback` and `--pdb` with stubtest (Stephen Morton, PR [18037](https://github.com/python/mypy/pull/18037))
* Verify `__all__` exists in stub (Sebastian Rittau, PR [18005](https://github.com/python/mypy/pull/18005))
* Stop telling people to use double underscores (Jelle Zijlstra, PR [17897](https://github.com/python/mypy/pull/17897))
Documentation Updates
* Update config file documentation (sobolevn, PR [18103](https://github.com/python/mypy/pull/18103))
* Improve contributor documentation for Windows (ag-tafe, PR [18097](https://github.com/python/mypy/pull/18097))
* Correct note about `--disallow-any-generics` flag in documentation (Abel Sen, PR [18055](https://github.com/python/mypy/pull/18055))
* Further caution against `--follow-imports=skip` (Shantanu, PR [18048](https://github.com/python/mypy/pull/18048))
* Fix the edit page button link in documentation (Kanishk Pachauri, PR [17933](https://github.com/python/mypy/pull/17933))
Other Notables Fixes and Improvements
* Show `Protocol` `__call__` for arguments with incompatible types (MechanicalConstruct, PR [18214](https://github.com/python/mypy/pull/18214))
* Make join and meet symmetric with `strict_optional` (MechanicalConstruct, PR [18227](https://github.com/python/mypy/pull/18227))
* Preserve block unreachablility when checking function definitions with constrained TypeVars (Brian Schubert, PR [18217](https://github.com/python/mypy/pull/18217))
* Do not include non-init fields in the synthesized `__replace__` method for dataclasses (Victorien, PR [18221](https://github.com/python/mypy/pull/18221))
* Disallow `TypeVar` constraints parameterized by type variables (Brian Schubert, PR [18186](https://github.com/python/mypy/pull/18186))
* Always complain about invalid varargs and varkwargs (Shantanu, PR [18207](https://github.com/python/mypy/pull/18207))
* Set default strict_optional state to True (Shantanu, PR [18198](https://github.com/python/mypy/pull/18198))
* Preserve type variable default None in type alias (Sukhorosov Aleksey, PR [18197](https://github.com/python/mypy/pull/18197))
* Add checks for invalid usage of continue/break/return in `except*` block (coldwolverine, PR [18132](https://github.com/python/mypy/pull/18132))
* Do not consider bare TypeVar not overlapping with None for reachability analysis (Stanislav Terliakov, PR [18138](https://github.com/python/mypy/pull/18138))
* Special case `types.DynamicClassAttribute` as property-like (Stephen Morton, PR [18150](https://github.com/python/mypy/pull/18150))
* Disallow bare `ParamSpec` in type aliases (Brian Schubert, PR [18174](https://github.com/python/mypy/pull/18174))
* Move long_description metadata to pyproject.toml (Marc Mueller, PR [18172](https://github.com/python/mypy/pull/18172))
* Support `==`-based narrowing of Optional (Christoph Tyralla, PR [18163](https://github.com/python/mypy/pull/18163))
* Allow TypedDict assignment of Required item to NotRequired ReadOnly item (Brian Schubert, PR [18164](https://github.com/python/mypy/pull/18164))
* Allow nesting of Annotated with TypedDict special forms inside TypedDicts (Brian Schubert, PR [18165](https://github.com/python/mypy/pull/18165))
* Infer generic type arguments for slice expressions (Brian Schubert, PR [18160](https://github.com/python/mypy/pull/18160))
* Fix checking of match sequence pattern against bounded type variables (Brian Schubert, PR [18091](https://github.com/python/mypy/pull/18091))
* Fix incorrect truthyness for Enum types and literals (David Salvisberg, PR [17337](https://github.com/python/mypy/pull/17337))
* Move static project metadata to pyproject.toml (Marc Mueller, PR [18146](https://github.com/python/mypy/pull/18146))
* Fallback to stdlib json if integer exceeds 64-bit range (q0w, PR [18148](https://github.com/python/mypy/pull/18148))
* Fix 'or' pattern structural matching exhaustiveness (yihong, PR [18119](https://github.com/python/mypy/pull/18119))
* Fix type inference of positional parameter in class pattern involving builtin subtype (Brian Schubert, PR [18141](https://github.com/python/mypy/pull/18141))
* Fix `[override]` error with no line number when argument node has no line number (Brian Schubert, PR [18122](https://github.com/python/mypy/pull/18122))
* Fix some dmypy crashes (Ivan Levkivskyi, PR [18098](https://github.com/python/mypy/pull/18098))
* Fix subtyping between instance type and overloaded (Shantanu, PR [18102](https://github.com/python/mypy/pull/18102))
* Clean up new_semantic_analyzer config (Shantanu, PR [18071](https://github.com/python/mypy/pull/18071))
* Issue warning for enum with no members in stub (Shantanu, PR [18068](https://github.com/python/mypy/pull/18068))
* Fix enum attributes are not members (Terence Honles, PR [17207](https://github.com/python/mypy/pull/17207))
* Fix crash when checking slice expression with step 0 in tuple index (Brian Schubert, PR [18063](https://github.com/python/mypy/pull/18063))
* Allow union-with-callable attributes to be overridden by methods (Brian Schubert, PR [18018](https://github.com/python/mypy/pull/18018))
* Emit `[mutable-override]` for covariant override of attribute with method (Brian Schubert, PR [18058](https://github.com/python/mypy/pull/18058))
* Support ParamSpec mapping with `functools.partial` (Stanislav Terliakov, PR [17355](https://github.com/python/mypy/pull/17355))
* Fix approved stub ignore, remove normpath (Shantanu, PR [18045](https://github.com/python/mypy/pull/18045))
* Make `disallow-any-unimported` flag invertible (Séamus Ó Ceanainn, PR [18030](https://github.com/python/mypy/pull/18030))
* Filter to possible package paths before trying to resolve a module (falsedrow, PR [18038](https://github.com/python/mypy/pull/18038))
* Fix overlap check for ParamSpec types (Jukka Lehtosalo, PR [18040](https://github.com/python/mypy/pull/18040))
* Do not prioritize ParamSpec signatures during overload resolution (Stanislav Terliakov, PR [18033](https://github.com/python/mypy/pull/18033))
* Fix ternary union for literals (Ivan Levkivskyi, PR [18023](https://github.com/python/mypy/pull/18023))
* Fix compatibility checks for conditional function definitions using decorators (Brian Schubert, PR [18020](https://github.com/python/mypy/pull/18020))
* TypeGuard should be bool not Any when matching TypeVar (Evgeniy Slobodkin, PR [17145](https://github.com/python/mypy/pull/17145))
* Fix convert-cache tool (Shantanu, PR [17974](https://github.com/python/mypy/pull/17974))
* Fix generator comprehension with mypyc (Shantanu, PR [17969](https://github.com/python/mypy/pull/17969))
* Fix crash issue when using shadowfile with pretty (Max Chang, PR [17894](https://github.com/python/mypy/pull/17894))
* Fix multiple nested classes with new generics syntax (Max Chang, PR [17820](https://github.com/python/mypy/pull/17820))
* Better error for `mypy -p package` without py.typed (Joe Gordon, PR [17908](https://github.com/python/mypy/pull/17908))
* Emit error for `raise NotImplemented` (Brian Schubert, PR [17890](https://github.com/python/mypy/pull/17890))
* Add `is_lvalue` attribute to AttributeContext (Brian Schubert, PR [17881](https://github.com/python/mypy/pull/17881))
Acknowledgements
Thanks to all mypy contributors who contributed to this release:
- aatle
- Abel Sen
- Advait Dixit
- ag-tafe
- Alex Waygood
- Ali Hamdan
- Brian Schubert
- Carlton Gibson
- Chad Dombrova
- Chelsea Durazo
- chiri
- Christoph Tyralla
- coldwolverine
- David Salvisberg
- Ekin Dursun
- Evgeniy Slobodkin
- falsedrow
- Gaurav Giri
- Ihor
- Ivan Levkivskyi
- jairov4
- Jannick Kremer
- Jared Hance
- Jelle Zijlstra
- jianghuyiyuan
- Joe Gordon
- John Doknjas
- Jukka Lehtosalo
- Kanishk Pachauri
- Marc Mueller
- Max Chang
- MechanicalConstruct
- Newbyte
- q0w
- Ruslan Sayfutdinov
- Sebastian Rittau
- Shantanu
- sobolevn
- Stanislav Terliakov
- Stephen Morton
- Sukhorosov Aleksey
- Séamus Ó Ceanainn
- Terence Honles
- Valentin Stanciu
- vasiliy
- Victorien
- yihong
I’d also like to thank my employer, Dropbox, for supporting mypy development.