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Mypy Release Notes

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Mypy 2.4

We've just uploaded mypy 2.4.0 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.

Python 3.15 Support

Mypy 2.4 supports running on Python 3.15 and type checking most Python 3.15 features. This includes the new builtin sentinel type for sentinel values (PEP 661), which mypy now supports (see below for details). Lazy imports (PEP 810) and unpacking in comprehensions (PEP 798) are also supported. Closed TypedDicts (PEP 728) have been supported since mypy 2.2, but the extra_items TypedDict argument, also introduced in PEP 728, is still unsupported. Support for extra_items will be added in a future mypy release.

Native Parser Enabled by Default

Mypy now uses the new native parser by default. It's based on the Ruff parser, and it's significantly faster than the legacy parser, which uses the stdlib ast module. The native parser also has other benefits:

• You can target newer Python versions and use recent Python syntax even when running mypy on an older Python version. For example, you can use --python-version 3.15 when running mypy on Python 3.14.
• Stub files can use syntax that is newer than the target Python version. For example, stubs can use the PEP 695 generic class syntax (class Box[T]: ...) when running on or targeting Python 3.10.
• Parallel type checking requires the native parser.

The legacy parser is still available through --no-native-parser, or native_parser = False in the config file (native_parser = false under [tool.mypy] in pyproject.toml). We are planning to remove the legacy parser in early 2027. If you run into a problem with the native parser, please report it on the issue tracker.

Unlike the legacy parser, the native parser doesn't support type comments for variables defined by for and with statements. These type comments are silently ignored, and the types of the variables are

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• 935ba8a Bump version to 2.4.0
• 334a678 Add link for PR 22066 in mypy 2.4 changelog (#22082)
• fe69660 Finalize mypy 2.4 changelog (#22080)
• 541fd87 Various mypy 2.4 changelog updates (#22077)
• b231182 Update native parser docs (#22078)
• 04fe42c Initial Changelog for Mypy 2.4 (#22071)
• 0617494 Quick fix for non UTF-8 encodings with new parser (#22066)
• b2f9b60 Bump librt to 0.16.0 (#22067)
• 9d798dc Sync typeshed (#22054)
• 0861bb6 Reduce max protocol stack size to 20 (#22053)
• Additional commits viewable in compare view

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