title	description
mypy configuration in MegaLinter	How to use mypy (configure, ignore files, ignore errors, help & version documentations) to analyze PYTHON files

MyPy is Python's premier static type checker that brings optional static typing to Python through gradual typing. It analyzes type annotations and infers types to catch bugs before runtime, bridging the gap between Python's dynamic nature and static analysis benefits.

Key Features:

Gradual Typing Support: Add type checking incrementally to existing codebases without requiring full annotation coverage
Type Inference: Advanced type inference engine that understands Python idioms and can deduce types even without explicit annotations
Protocol Support: Duck typing through protocols, enabling structural subtyping for flexible type checking
Generic Types: Full support for generic types, type variables, and complex type relationships
Plugin Architecture: Extensible with plugins for popular frameworks like Django, SQLAlchemy, and dataclasses
Incremental Checking: Fast incremental analysis that only re-checks modified files and their dependencies
Strict Mode Options: Configurable strictness levels from permissive to extremely strict type checking
Python Version Compatibility: Supports multiple Python versions and can check compatibility across versions

Note: If you don't use Python static typing, disable this linter by adding PYTHON_MYPY to DISABLE_LINTERS in your .mega-linter.yml config file.

mypy documentation

Version in MegaLinter: 1.18.2
Visit Official Web Site{target=_blank}
See How to configure mypy rules{target=_blank}
- If custom .mypy.ini config file isn't found, .mypy.ini{target=_blank} will be used
See How to disable mypy rules in files{target=_blank}

{target=_blank}

Configuration in MegaLinter

Enable mypy by adding PYTHON_MYPY in ENABLE_LINTERS variable
Disable mypy by adding PYTHON_MYPY in DISABLE_LINTERS variable

Variable	Description	Default value
PYTHON_MYPY_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
PYTHON_MYPY_COMMAND_REMOVE_ARGUMENTS	User custom arguments to remove from command line before calling the linter Ex: `-s --foo "bar"`
PYTHON_MYPY_FILTER_REGEX_INCLUDE	Custom regex including filter Ex: `(src\|lib)`	Include every file
PYTHON_MYPY_FILTER_REGEX_EXCLUDE	Custom regex excluding filter Ex: `(test\|examples)`	Exclude no file
PYTHON_MYPY_CLI_LINT_MODE	Override default CLI lint mode - `file`: Calls the linter for each file - `list_of_files`: Call the linter with the list of files as argument - `project`: Call the linter from the root of the project	`list_of_files`
PYTHON_MYPY_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".py", ".pyi", ".ipynb"]`
PYTHON_MYPY_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
PYTHON_MYPY_PRE_COMMANDS	List of bash commands to run before the linter	None
PYTHON_MYPY_POST_COMMANDS	List of bash commands to run after the linter	None
PYTHON_MYPY_UNSECURED_ENV_VARIABLES	List of env variables explicitly not filtered before calling PYTHON_MYPY and its pre/post commands	None
PYTHON_MYPY_CONFIG_FILE	mypy configuration file name Use `LINTER_DEFAULT` to let the linter find it	`.mypy.ini`
PYTHON_MYPY_RULES_PATH	Path where to find linter configuration file	Workspace folder, then MegaLinter default rules
PYTHON_MYPY_DISABLE_ERRORS	Run linter but consider errors as warnings	`false`
PYTHON_MYPY_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`
PYTHON_MYPY_CLI_EXECUTABLE	Override CLI executable	`['mypy']`

IDE Integration

Use mypy in your favorite IDE to catch errors before MegaLinter !

IDE	Extension Name	Install
Emacs	Flycheck mypy	Visit Web Site{target=_blank}
IDEA	mypy-official	Visit Web Site{target=_blank}
Sublime Text	SublimeLinter-contrib-mypy	Visit Web Site{target=_blank}
vim	Ale	Visit Web Site{target=_blank}
vim	Syntastic	Visit Web Site{target=_blank}
Visual Studio Code	Mypy	{target=_blank}

MegaLinter Flavors

This linter is available in the following flavors

Flavor	Description	Embedded linters
all	Default MegaLinter Flavor	127
cupcake	MegaLinter for the most commonly used languages	88
python	Optimized for PYTHON based projects	65

Behind the scenes

How are identified applicable files

File extensions: .py, .pyi, .ipynb

How the linting is performed

mypy is called once with the list of files as arguments (list_of_files CLI lint mode)

Example calls

mypy myfile.py

mypy --config-file .mypy.yml myfile.py

Help content

usage: mypy [-h] [-v] [-V] [more options; see below]
            [-m MODULE] [-p PACKAGE] [-c PROGRAM_TEXT] [files ...]

Mypy is a program that will type check your Python code.

Pass in any files or folders you want to type check. Mypy will
recursively traverse any provided folders to find .py files:

    $ mypy my_program.py my_src_folder

For more information on getting started, see:

- https://mypy.readthedocs.io/en/stable/getting_started.html

For more details on both running mypy and using the flags below, see:

- https://mypy.readthedocs.io/en/stable/running_mypy.html
- https://mypy.readthedocs.io/en/stable/command_line.html

You can also use a config file to configure mypy instead of using
command line flags. For more details, see:

- https://mypy.readthedocs.io/en/stable/config_file.html

options:
  --enable-incomplete-feature {InlineTypedDict,PreciseTupleTypes}
                            Enable support of incomplete/experimental features
                            for early preview

Optional arguments:
  -h, --help                Show this help message and exit
  -v, --verbose             More verbose messages
  -V, --version             Show program's version number and exit
  -O, --output FORMAT       Set a custom output format

Config file:
  Use a config file instead of command line arguments. This is useful if you
  are using many flags or want to set different options per each module.

  --config-file CONFIG_FILE
                            Configuration file, must have a [mypy] section
                            (defaults to mypy.ini, .mypy.ini, pyproject.toml,
                            setup.cfg)
  --warn-unused-configs     Warn about unused '[mypy-<pattern>]' or
                            '[[tool.mypy.overrides]]' config sections
                            (inverse: --no-warn-unused-configs)

Import discovery:
  Configure how imports are discovered and followed.

  --no-namespace-packages   Disable support for namespace packages (PEP 420,
                            __init__.py-less) (inverse: --namespace-packages)
  --ignore-missing-imports  Silently ignore imports of missing modules
  --follow-untyped-imports  Typecheck modules without stubs or py.typed marker
  --follow-imports {normal,silent,skip,error}
                            How to treat imports (default normal)
  --python-executable EXECUTABLE
                            Python executable used for finding PEP 561
                            compliant installed packages and stubs
  --no-site-packages        Do not search for installed PEP 561 compliant
                            packages
  --no-silence-site-packages
                            Do not silence errors in PEP 561 compliant
                            installed packages
  --junit-format {global,per_file}
                            If --junit-xml is set, specifies format. global:
                            single test with all errors; per_file: one test
                            entry per file with failures

Platform configuration:
  Type check code assuming it will be run under certain runtime conditions.
  By default, mypy assumes your code will be run using the same operating
  system and Python version you are using to run mypy itself.

  --python-version x.y      Type check code assuming it will be running on
                            Python x.y
  --platform PLATFORM       Type check special-cased code for the given OS
                            platform (defaults to sys.platform)
  --always-true NAME        Additional variable to be considered True (may be
                            repeated)
  --always-false NAME       Additional variable to be considered False (may be
                            repeated)

Disallow dynamic typing:
  Disallow the use of the dynamic 'Any' type under certain conditions.

  --disallow-any-expr       Disallow all expressions that have type Any
  --disallow-any-decorated  Disallow functions that have Any in their
                            signature after decorator transformation
  --disallow-any-explicit   Disallow explicit Any in type positions
  --disallow-any-generics   Disallow usage of generic types that do not
                            specify explicit type parameters (inverse:
                            --allow-any-generics)
  --disallow-any-unimported
                            Disallow Any types resulting from unfollowed
                            imports (inverse: --allow-any-unimported)
  --disallow-subclassing-any
                            Disallow subclassing values of type 'Any' when
                            defining classes (inverse: --allow-subclassing-
                            any)

Untyped definitions and calls:
  Configure how untyped definitions and calls are handled. Note: by default,
  mypy ignores any untyped function definitions and assumes any calls to
  such functions have a return type of 'Any'.

  --disallow-untyped-calls  Disallow calling functions without type
                            annotations from functions with type annotations
                            (inverse: --allow-untyped-calls)
  --untyped-calls-exclude MODULE
                            Disable --disallow-untyped-calls for
                            functions/methods coming from specific package,
                            module, or class
  --disallow-untyped-defs   Disallow defining functions without type
                            annotations or with incomplete type annotations
                            (inverse: --allow-untyped-defs)
  --disallow-incomplete-defs
                            Disallow defining functions with incomplete type
                            annotations (while still allowing entirely
                            unannotated definitions) (inverse: --allow-
                            incomplete-defs)
  --check-untyped-defs      Type check the interior of functions without type
                            annotations (inverse: --no-check-untyped-defs)
  --disallow-untyped-decorators
                            Disallow decorating typed functions with untyped
                            decorators (inverse: --allow-untyped-decorators)

None and Optional handling:
  Adjust how values of type 'None' are handled. For more context on how mypy
  handles values of type 'None', see:
  https://mypy.readthedocs.io/en/stable/kinds_of_types.html#optional-types-
  and-the-none-type

  --implicit-optional       Assume arguments with default values of None are
                            Optional (inverse: --no-implicit-optional)
  --no-strict-optional      Disable strict Optional checks (inverse: --strict-
                            optional)

Configuring warnings:
  Detect code that is sound but redundant or problematic.

  --warn-redundant-casts    Warn about casting an expression to its inferred
                            type (inverse: --no-warn-redundant-casts)
  --warn-unused-ignores     Warn about unneeded '# type: ignore' comments
                            (inverse: --no-warn-unused-ignores)
  --no-warn-no-return       Do not warn about functions that end without
                            returning (inverse: --warn-no-return)
  --warn-return-any         Warn about returning values of type Any from non-
                            Any typed functions (inverse: --no-warn-return-
                            any)
  --warn-unreachable        Warn about statements or expressions inferred to
                            be unreachable (inverse: --no-warn-unreachable)
  --report-deprecated-as-note
                            Report importing or using deprecated features as
                            notes instead of errors (inverse: --no-report-
                            deprecated-as-note)
  --deprecated-calls-exclude MODULE
                            Disable deprecated warnings for functions/methods
                            coming from specific package, module, or class

Miscellaneous strictness flags:
  --allow-untyped-globals   Suppress toplevel errors caused by missing
                            annotations (inverse: --disallow-untyped-globals)
  --allow-redefinition      Allow restricted, unconditional variable
                            redefinition with a new type (inverse: --disallow-
                            redefinition)
  --allow-redefinition-new  Allow more flexible variable redefinition
                            semantics (experimental) (inverse: --disallow-
                            redefinition-new)
  --no-implicit-reexport    Treat imports as private unless aliased (inverse:
                            --implicit-reexport)
  --strict-equality         Prohibit equality, identity, and container checks
                            for non-overlapping types (except `None`)
                            (inverse: --no-strict-equality)
  --strict-equality-for-none
                            Extend `--strict-equality` for `None` checks
                            (inverse: --no-strict-equality-for-none)
  --strict-bytes            Disable treating bytearray and memoryview as
                            subtypes of bytes (inverse: --no-strict-bytes)
  --extra-checks            Enable additional checks that are technically
                            correct but may be impractical in real code. For
                            example, this prohibits partial overlap in
                            TypedDict updates, and makes arguments prepended
                            via Concatenate positional-only (inverse: --no-
                            extra-checks)
  --strict                  Strict mode; enables the following flags: --warn-
                            unused-configs, --disallow-any-generics,
                            --disallow-subclassing-any, --disallow-untyped-
                            calls, --disallow-untyped-defs, --disallow-
                            incomplete-defs, --check-untyped-defs, --disallow-
                            untyped-decorators, --warn-redundant-casts,
                            --warn-unused-ignores, --warn-return-any, --no-
                            implicit-reexport, --strict-equality, --strict-
                            bytes, --extra-checks
  --disable-error-code NAME
                            Disable a specific error code
  --enable-error-code NAME  Enable a specific error code

Configuring error messages:
  Adjust the amount of detail shown in error messages.

  --show-error-context      Precede errors with "note:" messages explaining
                            context (inverse: --hide-error-context)
  --show-column-numbers     Show column numbers in error messages (inverse:
                            --hide-column-numbers)
  --show-error-end          Show end line/end column numbers in error
                            messages. This implies --show-column-numbers
                            (inverse: --hide-error-end)
  --hide-error-codes        Hide error codes in error messages (inverse:
                            --show-error-codes)
  --show-error-code-links   Show links to error code documentation (inverse:
                            --hide-error-code-links)
  --pretty                  Use visually nicer output in error messages: Use
                            soft word wrap, show source code snippets, and
                            show error location markers (inverse: --no-pretty)
  --no-color-output         Do not colorize error messages (inverse: --color-
                            output)
  --no-error-summary        Do not show error stats summary (inverse: --error-
                            summary)
  --show-absolute-path      Show absolute paths to files (inverse: --hide-
                            absolute-path)

Incremental mode:
  Adjust how mypy incrementally type checks and caches modules. Mypy caches
  type information about modules into a cache to let you speed up future
  invocations of mypy. Also see mypy's daemon mode:
  mypy.readthedocs.io/en/stable/mypy_daemon.html#mypy-daemon

  --no-incremental          Disable module cache (inverse: --incremental)
  --cache-dir DIR           Store module cache info in the given folder in
                            incremental mode (defaults to '.mypy_cache')
  --sqlite-cache            Use a sqlite database to store the cache (inverse:
                            --no-sqlite-cache)
  --cache-fine-grained      Include fine-grained dependency information in the
                            cache for the mypy daemon
  --fixed-format-cache      Use experimental fast and compact fixed format
                            cache
  --skip-version-check      Allow using cache written by older mypy version
  --skip-cache-mtime-checks
                            Skip cache internal consistency checks based on
                            mtime

Advanced options:
  Debug and customize mypy internals.

  --pdb                     Invoke pdb on fatal error
  --show-traceback, --tb    Show traceback on fatal error
  --raise-exceptions        Raise exception on fatal error
  --custom-typing-module MODULE
                            Use a custom typing module
  --custom-typeshed-dir DIR
                            Use the custom typeshed in DIR
  --warn-incomplete-stub    Warn if missing type annotation in typeshed, only
                            relevant with --disallow-untyped-defs or
                            --disallow-incomplete-defs enabled (inverse: --no-
                            warn-incomplete-stub)
  --shadow-file SOURCE_FILE SHADOW_FILE
                            When encountering SOURCE_FILE, read and type check
                            the contents of SHADOW_FILE instead.

Report generation:
  Generate a report in the specified format.

  --any-exprs-report DIR
  --cobertura-xml-report DIR
  --html-report DIR
  --linecount-report DIR
  --linecoverage-report DIR
  --lineprecision-report DIR
  --txt-report DIR
  --xml-report DIR
  --xslt-html-report DIR
  --xslt-txt-report DIR

Miscellaneous:
  --junit-xml JUNIT_XML     Write junit.xml to the given file
  --find-occurrences CLASS.MEMBER
                            Print out all usages of a class member
                            (experimental)
  --scripts-are-modules     Script x becomes module x instead of __main__
  --install-types           Install detected missing library stub packages
                            using pip (inverse: --no-install-types)
  --non-interactive         Install stubs without asking for confirmation and
                            hide errors, with --install-types (inverse:
                            --interactive)

Running code:
  Specify the code you want to type check. For more details, see
  mypy.readthedocs.io/en/stable/running_mypy.html#running-mypy

  --explicit-package-bases  Use current directory and MYPYPATH to determine
                            module names of files passed (inverse: --no-
                            explicit-package-bases)
  --exclude PATTERN         Regular expression to match file names, directory
                            names or paths which mypy should ignore while
                            recursively discovering files to check, e.g.
                            --exclude '/setup\.py$'. May be specified more
                            than once, eg. --exclude a --exclude b
  --exclude-gitignore       Use .gitignore file(s) to exclude files from
                            checking (in addition to any explicit --exclude if
                            present) (inverse: --no-exclude-gitignore)
  -m, --module MODULE       Type-check module; can repeat for more modules
  -p, --package PACKAGE     Type-check package recursively; can be repeated
  -c, --command PROGRAM_TEXT
                            Type-check program passed in as string
  files                     Type-check given files or directories

Environment variables:
  Define MYPYPATH for additional module search path entries.
  Define MYPY_CACHE_DIR to override configuration cache_dir path.

Installation on mega-linter Docker image

Dockerfile commands :

# renovate: datasource=pypi depName=mypy
ARG PIP_MYPY_VERSION=1.18.2
ENV MYPY_CACHE_DIR=/tmp

PIP packages (Python):
- mypy==1.18.2

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