Mypy is a static type checker for Python, enabling optional static typing to improve code quality and maintainability. As of version 1.19.1, it supports Python 3.9 and later, with regular updates and a stable release cadence.
pip install mypyVerified import paths — ran on the pinned version, not inferred.
Integrate Mypy into your Python application by importing 'mypy.api' and calling the 'run' function with command-line arguments. This allows programmatic access to Mypy's type checking capabilities.
Upgrade to Python 3.8 or later to maintain compatibility.
Install 'typing_extensions' to use these features on older Python versions.
Ensure that the 'mypy' command is followed by the path to the files, modules, or packages you intend to type-check, for example: 'mypy my_script.py' or 'mypy -m my_package'.
Ensure the 'mypy' command is invoked with a target, such as 'mypy your_module.py', 'mypy --package your_package', or 'mypy --module your_module'.
Install the module (e.g., `pip install foo`), install its type stubs (e.g., `pip install types-foo` or `mypy --install-types`), add the module's parent directory to `MYPYPATH`, or configure `mypy.ini` with `ignore_missing_imports = True` for the specific module (e.g., `[mypy-foo.*] ignore_missing_imports = True`).
Ensure the assigned value's type matches the variable's expected type, or explicitly annotate the variable with a `Union` type if it can legitimately hold different types, or use `cast()` if you are certain about the type and want to override Mypy.
Add an explicit type annotation to the variable, especially for empty containers (e.g., `my_list: list[str] = []` or `my_dict: dict[str, int] = {}`).Correct any typos in the name, ensure the item is imported from the correct module, or define the name before its first use.
Ensure all code paths within the function explicitly return a value consistent with its return type annotation, or change the return type annotation to `None` if the function is not meant to return anything.