Sourced from mypy's changelog.

Mypy Release Notes

Next Release

Mypy 2.2

We've just uploaded mypy 2.2.0 to the Python Package Index (PyPI). Mypy is a static type checker for Python. This release includes new features, performance improvements 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.

Support for Closed TypedDicts (PEP 728)

Mypy now supports closed TypedDicts as specified in PEP 728. A closed TypedDict cannot have extra keys beyond those explicitly defined. This allows the type checker to determine that certain operations are safe when they otherwise wouldn't be due to the potential presence of unknown keys.

You can use the closed keyword argument with TypedDict:

HasName = TypedDict("HasName", {"name": str})
HasOnlyName = TypedDict("HasOnlyName", {"name": str}, closed=True)
Movie = TypedDict("Movie", {"name": str, "year": int})
movie: Movie = {"name": "Nimona", "year": 2023}
has_name: HasName = movie  # OK: HasName is open (default)
has_only_name: HasOnlyName = movie  # Error: HasOnlyName is closed and Movie has extra "year" key

Closed TypedDicts enable more precise type checking because the type checker knows exactly which keys are present. This is particularly useful when working with TypedDict unions or when you want to ensure that a TypedDict conforms to an exact shape.

The closed keyword also enables safe type narrowing with in checks:

Book = TypedDict('Book', {'book': str}, closed=True)
DVD = TypedDict('DVD', {'dvd': str}, closed=True)
type Inventory = Book | DVD
def print_type(inventory: Inventory) -> None:
if "book" in inventory:
# Type is narrowed to Book here - safe because DVD is closed
print(inventory["book"])
else:
# Type is narrowed to DVD here
print(inventory["dvd"])
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• b3c4a5b Mark release
• 396f508 [Chore] Update changelog for 2.2 (#21691)
• 9592a9e Upload wasm wheels to PyPI (#21671)
• 1dc6962 Bump ast-serialize to 0.6.0 (#21664)
• 96a7913 Bump librt to 0.12.0 (#21663)
• 5ef0902 Fix the exportjson tool (.ff cache to .json conversion) (#21628)
• 8d621ad Support --shadow-file with --native-parser (#21623)
• 74ecdd8 Sync typeshed (#21612)
• 0cd1541 [mypyc] Make function wrappers thread-safe on free-threaded builds (#21620)
• 22a9cfd [mypyc] Make list remove and index thread-safe on free-threaded builds (#21614)
• Additional commits viewable in compare view

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