The mypy configuration file#

Mypy supports reading configuration settings from a file. By default it uses the file mypy.ini with a fallback to .mypy.ini, then pyproject.toml, then setup.cfg in the current directory, then $XDG_CONFIG_HOME/mypy/config, then ~/.config/mypy/config, and finally .mypy.ini in the user home directory if none of them are found; the --config-file command-line flag can be used to read a different file instead (see Config file).

It is important to understand that there is no merging of configuration files, as it would lead to ambiguity. The --config-file flag has the highest precedence and must be correct; otherwise mypy will report an error and exit. Without command line option, mypy will look for configuration files in the above mentioned order.

Most flags correspond closely to command-line flags but there are some differences in flag names and some flags may take a different value based on the module being processed.

Some flags support user home directory and environment variable expansion. To refer to the user home directory, use ~ at the beginning of the path. To expand environment variables use $VARNAME or ${VARNAME}.

Config file format#

The configuration file format is the usual ini file format. It should contain section names in square brackets and flag settings of the form NAME = VALUE. Comments start with # characters.

  • A section named [mypy] must be present. This specifies the global flags.

  • Additional sections named [mypy-PATTERN1,PATTERN2,...] may be present, where PATTERN1, PATTERN2, etc., are comma-separated patterns of fully-qualified module names, with some components optionally replaced by the ‘*’ character (e.g. foo.bar, foo.bar.*, foo.*.baz). These sections specify additional flags that only apply to modules whose name matches at least one of the patterns.

    A pattern of the form qualified_module_name matches only the named module, while dotted_module_name.* matches dotted_module_name and any submodules (so foo.bar.* would match all of foo.bar, foo.bar.baz, and foo.bar.baz.quux).

    Patterns may also be “unstructured” wildcards, in which stars may appear in the middle of a name (e.g site.*.migrations.*). Stars match zero or more module components (so site.*.migrations.* can match site.migrations).

    When options conflict, the precedence order for configuration is:

    1. Inline configuration in the source file

    2. Sections with concrete module names (foo.bar)

    3. Sections with “unstructured” wildcard patterns (foo.*.baz), with sections later in the configuration file overriding sections earlier.

    4. Sections with “well-structured” wildcard patterns (foo.bar.*), with more specific overriding more general.

    5. Command line options.

    6. Top-level configuration file options.

The difference in precedence order between “structured” patterns (by specificity) and “unstructured” patterns (by order in the file) is unfortunate, and is subject to change in future versions.

Note

The warn_unused_configs flag may be useful to debug misspelled section names.

Note

Configuration flags are liable to change between releases.

Per-module and global options#

Some of the config options may be set either globally (in the [mypy] section) or on a per-module basis (in sections like [mypy-foo.bar]).

If you set an option both globally and for a specific module, the module configuration options take precedence. This lets you set global defaults and override them on a module-by-module basis. If multiple pattern sections match a module, the options from the most specific section are used where they disagree.

Some other options, as specified in their description, may only be set in the global section ([mypy]).

Inverting option values#

Options that take a boolean value may be inverted by adding no_ to their name or by (when applicable) swapping their prefix from disallow to allow (and vice versa).

Examples#

Here is an example of a mypy.ini file. To use this config file, place it at the root of your repo and run mypy.

# Global options:

[mypy]
warn_return_any = True
warn_unused_configs = True

# Per-module options:

[mypy-mycode.foo.*]
disallow_untyped_defs = True

[mypy-mycode.bar]
warn_return_any = False

[mypy-somelibrary]
ignore_missing_imports = True

This config file specifies two global options in the [mypy] section. These two options will:

  1. Report an error whenever a function returns a value that is inferred to have type Any.

  2. Report any config options that are unused by mypy. (This will help us catch typos when making changes to our config file).

Next, this module specifies three per-module options. The first two options change how mypy type checks code in mycode.foo.* and mycode.bar, which we assume here are two modules that you wrote. The final config option changes how mypy type checks somelibrary, which we assume here is some 3rd party library you’ve installed and are importing. These options will:

  1. Selectively disallow untyped function definitions only within the mycode.foo package – that is, only for function definitions defined in the mycode/foo directory.

  2. Selectively disable the “function is returning any” warnings within mycode.bar only. This overrides the global default we set earlier.

  3. Suppress any error messages generated when your codebase tries importing the module somelibrary. This is useful if somelibrary is some 3rd party library missing type hints.

Import discovery#

For more information, see the Import discovery section of the command line docs.

mypy_path#
Type

string

Specifies the paths to use, after trying the paths from MYPYPATH environment variable. Useful if you’d like to keep stubs in your repo, along with the config file. Multiple paths are always separated with a : or , regardless of the platform. User home directory and environment variables will be expanded.

Relative paths are treated relative to the working directory of the mypy command, not the config file. Use the MYPY_CONFIG_FILE_DIR environment variable to refer to paths relative to the config file (e.g. mypy_path = $MYPY_CONFIG_FILE_DIR/src).

This option may only be set in the global section ([mypy]).

Note: On Windows, use UNC paths to avoid using : (e.g. \\127.0.0.1\X$\MyDir where X is the drive letter).

files#
Type

comma-separated list of strings

A comma-separated list of paths which should be checked by mypy if none are given on the command line. Supports recursive file globbing using glob, where * (e.g. *.py) matches files in the current directory and **/ (e.g. **/*.py) matches files in any directories below the current one. User home directory and environment variables will be expanded.

This option may only be set in the global section ([mypy]).

exclude#
Type

regular expression

A regular expression that matches file names, directory names and paths which mypy should ignore while recursively discovering files to check. Use forward slashes (/) as directory separators on all platforms.

[mypy]
exclude = (?x)(
    ^one\.py$    # files named "one.py"
    | two\.pyi$  # or files ending with "two.pyi"
    | ^three\.   # or files starting with "three."
  )

Crafting a single regular expression that excludes multiple files while remaining human-readable can be a challenge. The above example demonstrates one approach. (?x) enables the VERBOSE flag for the subsequent regular expression, which ignores most whitespace and supports comments. The above is equivalent to: (^one\.py$|two\.pyi$|^three\.).

For more details, see --exclude.

This option may only be set in the global section ([mypy]).

Note

Note that the TOML equivalent differs slightly. It can be either a single string (including a multi-line string) – which is treated as a single regular expression – or an array of such strings. The following TOML examples are equivalent to the above INI example.

Array of strings:

[tool.mypy]
exclude = [
    "^one\\.py$",  # TOML's double-quoted strings require escaping backslashes
    'two\.pyi$',  # but TOML's single-quoted strings do not
    '^three\.',
]

A single, multi-line string:

[tool.mypy]
exclude = '''(?x)(
    ^one\.py$    # files named "one.py"
    | two\.pyi$  # or files ending with "two.pyi"
    | ^three\.   # or files starting with "three."
)'''  # TOML's single-quoted strings do not require escaping backslashes

See Using a pyproject.toml file.

namespace_packages#
Type

boolean

Default

True

Enables PEP 420 style namespace packages. See the corresponding flag --no-namespace-packages for more information.

This option may only be set in the global section ([mypy]).

explicit_package_bases#
Type

boolean

Default

False

This flag tells mypy that top-level packages will be based in either the current directory, or a member of the MYPYPATH environment variable or mypy_path config option. This option is only useful in the absence of __init__.py. See Mapping file paths to modules for details.

This option may only be set in the global section ([mypy]).

ignore_missing_imports#
Type

boolean

Default

False

Suppresses error messages about imports that cannot be resolved.

If this option is used in a per-module section, the module name should match the name of the imported module, not the module containing the import statement.

follow_imports#
Type

string

Default

normal

Directs what to do with imports when the imported module is found as a .py file and not part of the files, modules and packages provided on the command line.

The four possible values are normal, silent, skip and error. For explanations see the discussion for the --follow-imports command line flag.

Using this option in a per-module section (potentially with a wildcard, as described at the top of this page) is a good way to prevent mypy from checking portions of your code.

If this option is used in a per-module section, the module name should match the name of the imported module, not the module containing the import statement.

follow_imports_for_stubs#
Type

boolean

Default

False

Determines whether to respect the follow_imports setting even for stub (.pyi) files.

Used in conjunction with follow_imports=skip, this can be used to suppress the import of a module from typeshed, replacing it with Any.

Used in conjunction with follow_imports=error, this can be used to make any use of a particular typeshed module an error.

Note

This is not supported by the mypy daemon.

python_executable#
Type

string

Specifies the path to the Python executable to inspect to collect a list of available PEP 561 packages. User home directory and environment variables will be expanded. Defaults to the executable used to run mypy.

This option may only be set in the global section ([mypy]).

no_site_packages#
Type

bool

Default

False

Disables using type information in installed packages (see PEP 561). This will also disable searching for a usable Python executable. This acts the same as --no-site-packages command line flag.

no_silence_site_packages#
Type

boolean

Default

False

Enables reporting error messages generated within installed packages (see PEP 561 for more details on distributing type information). Those error messages are suppressed by default, since you are usually not able to control errors in 3rd party code.

This option may only be set in the global section ([mypy]).

Platform configuration#

python_version#
Type

string

Specifies the Python version used to parse and check the target program. The string should be in the format MAJOR.MINOR – for example 2.7. The default is the version of the Python interpreter used to run mypy.

This option may only be set in the global section ([mypy]).

platform#
Type

string

Specifies the OS platform for the target program, for example darwin or win32 (meaning OS X or Windows, respectively). The default is the current platform as revealed by Python’s sys.platform variable.

This option may only be set in the global section ([mypy]).

always_true#
Type

comma-separated list of strings

Specifies a list of variables that mypy will treat as compile-time constants that are always true.

always_false#
Type

comma-separated list of strings

Specifies a list of variables that mypy will treat as compile-time constants that are always false.

Disallow dynamic typing#

For more information, see the Disallow dynamic typing section of the command line docs.

disallow_any_unimported#
Type

boolean

Default

False

Disallows usage of types that come from unfollowed imports (anything imported from an unfollowed import is automatically given a type of Any).

disallow_any_expr#
Type

boolean

Default

False

Disallows all expressions in the module that have type Any.

disallow_any_decorated#
Type

boolean

Default

False

Disallows functions that have Any in their signature after decorator transformation.

disallow_any_explicit#
Type

boolean

Default

False

Disallows explicit Any in type positions such as type annotations and generic type parameters.

disallow_any_generics#
Type

boolean

Default

False

Disallows usage of generic types that do not specify explicit type parameters.

disallow_subclassing_any#
Type

boolean

Default

False

Disallows subclassing a value of type Any.

Untyped definitions and calls#

For more information, see the Untyped definitions and calls section of the command line docs.

disallow_untyped_calls#
Type

boolean

Default

False

Disallows calling functions without type annotations from functions with type annotations.

disallow_untyped_defs#
Type

boolean

Default

False

Disallows defining functions without type annotations or with incomplete type annotations.

disallow_incomplete_defs#
Type

boolean

Default

False

Disallows defining functions with incomplete type annotations.

check_untyped_defs#
Type

boolean

Default

False

Type-checks the interior of functions without type annotations.

disallow_untyped_decorators#
Type

boolean

Default

False

Reports an error whenever a function with type annotations is decorated with a decorator without annotations.

None and Optional handling#

For more information, see the None and Optional handling section of the command line docs.

implicit_optional#
Type

boolean

Default

False

Causes mypy to treat arguments with a None default value as having an implicit Optional type.

Note: This was True by default in mypy versions 0.980 and earlier.

strict_optional#
Type

boolean

Default

True

Enables or disables strict Optional checks. If False, mypy treats None as compatible with every type.

Note: This was False by default in mypy versions earlier than 0.600.

Configuring warnings#

For more information, see the Configuring warnings section of the command line docs.

warn_redundant_casts#
Type

boolean

Default

False

Warns about casting an expression to its inferred type.

This option may only be set in the global section ([mypy]).

warn_unused_ignores#
Type

boolean

Default

False

Warns about unneeded # type: ignore comments.

warn_no_return#
Type

boolean

Default

True

Shows errors for missing return statements on some execution paths.

warn_return_any#
Type

boolean

Default

False

Shows a warning when returning a value with type Any from a function declared with a non- Any return type.

warn_unreachable#
Type

boolean

Default

False

Shows a warning when encountering any code inferred to be unreachable or redundant after performing type analysis.

Suppressing errors#

Note: these configuration options are available in the config file only. There is no analog available via the command line options.

ignore_errors#
Type

boolean

Default

False

Ignores all non-fatal errors.

Miscellaneous strictness flags#

For more information, see the Miscellaneous strictness flags section of the command line docs.

allow_untyped_globals#
Type

boolean

Default

False

Causes mypy to suppress errors caused by not being able to fully infer the types of global and class variables.

allow_redefinition#
Type

boolean

Default

False

Allows variables to be redefined with an arbitrary type, as long as the redefinition is in the same block and nesting level as the original definition. Example where this can be useful:

def process(items: list[str]) -> None:
    # 'items' has type list[str]
    items = [item.split() for item in items]
    # 'items' now has type list[list[str]]

The variable must be used before it can be redefined:

def process(items: list[str]) -> None:
   items = "mypy"  # invalid redefinition to str because the variable hasn't been used yet
   print(items)
   items = "100"  # valid, items now has type str
   items = int(items)  # valid, items now has type int
local_partial_types#
Type

boolean

Default

False

Disallows inferring variable type for None from two assignments in different scopes. This is always implicitly enabled when using the mypy daemon.

disable_error_code#
Type

comma-separated list of strings

Allows disabling one or multiple error codes globally.

enable_error_code#
Type

comma-separated list of strings

Allows enabling one or multiple error codes globally.

Note: This option will override disabled error codes from the disable_error_code option.

implicit_reexport#
Type

boolean

Default

True

By default, imported values to a module are treated as exported and mypy allows other modules to import them. When false, mypy will not re-export unless the item is imported using from-as or is included in __all__. Note that mypy treats stub files as if this is always disabled. For example:

# This won't re-export the value
from foo import bar
# This will re-export it as bar and allow other modules to import it
from foo import bar as bar
# This will also re-export bar
from foo import bar
__all__ = ['bar']
strict_concatenate#
Type

boolean

Default

False

Make arguments prepended via Concatenate be truly positional-only.

strict_equality#
type

boolean

default

False

Prohibit equality checks, identity checks, and container checks between non-overlapping types.

strict#
type

boolean

default

False

Enable all optional error checking flags. You can see the list of flags enabled by strict mode in the full mypy --help output.

Note: the exact list of flags enabled by strict may change over time.

Configuring error messages#

For more information, see the Configuring error messages section of the command line docs.

These options may only be set in the global section ([mypy]).

show_error_context#
Type

boolean

Default

False

Prefixes each error with the relevant context.

show_column_numbers#
Type

boolean

Default

False

Shows column numbers in error messages.

hide_error_codes#
Type

boolean

Default

False

Hides error codes in error messages. See Error codes for more information.

pretty#
Type

boolean

Default

False

Use visually nicer output in error messages: use soft word wrap, show source code snippets, and show error location markers.

color_output#
Type

boolean

Default

True

Shows error messages with color enabled.

error_summary#
Type

boolean

Default

True

Shows a short summary line after error messages.

show_absolute_path#
Type

boolean

Default

False

Show absolute paths to files.

Incremental mode#

These options may only be set in the global section ([mypy]).

incremental#
Type

boolean

Default

True

Enables incremental mode.

cache_dir#
Type

string

Default

.mypy_cache

Specifies the location where mypy stores incremental cache info. User home directory and environment variables will be expanded. This setting will be overridden by the MYPY_CACHE_DIR environment variable.

Note that the cache is only read when incremental mode is enabled but is always written to, unless the value is set to /dev/null (UNIX) or nul (Windows).

sqlite_cache#
Type

boolean

Default

False

Use an SQLite database to store the cache.

cache_fine_grained#
Type

boolean

Default

False

Include fine-grained dependency information in the cache for the mypy daemon.

skip_version_check#
Type

boolean

Default

False

Makes mypy use incremental cache data even if it was generated by a different version of mypy. (By default, mypy will perform a version check and regenerate the cache if it was written by older versions of mypy.)

skip_cache_mtime_checks#
Type

boolean

Default

False

Skip cache internal consistency checks based on mtime.

Advanced options#

These options may only be set in the global section ([mypy]).

plugins#
Type

comma-separated list of strings

A comma-separated list of mypy plugins. See Extending mypy using plugins.

pdb#
Type

boolean

Default

False

Invokes pdb on fatal error.

show_traceback#
Type

boolean

Default

False

Shows traceback on fatal error.

raise_exceptions#
Type

boolean

Default

False

Raise exception on fatal error.

custom_typing_module#
Type

string

Specifies a custom module to use as a substitute for the typing module.

custom_typeshed_dir#
Type

string

This specifies the directory where mypy looks for standard library typeshed stubs, instead of the typeshed that ships with mypy. This is primarily intended to make it easier to test typeshed changes before submitting them upstream, but also allows you to use a forked version of typeshed.

User home directory and environment variables will be expanded.

Note that this doesn’t affect third-party library stubs. To test third-party stubs, for example try MYPYPATH=stubs/six mypy ....

warn_incomplete_stub#
Type

boolean

Default

False

Warns about missing type annotations in typeshed. This is only relevant in combination with disallow_untyped_defs or disallow_incomplete_defs.

Report generation#

If these options are set, mypy will generate a report in the specified format into the specified directory.

any_exprs_report#
Type

string

Causes mypy to generate a text file report documenting how many expressions of type Any are present within your codebase.

cobertura_xml_report#
Type

string

Causes mypy to generate a Cobertura XML type checking coverage report.

To generate this report, you must either manually install the lxml library or specify mypy installation with the setuptools extra mypy[reports].

html_report / xslt_html_report#
Type

string

Causes mypy to generate an HTML type checking coverage report.

To generate this report, you must either manually install the lxml library or specify mypy installation with the setuptools extra mypy[reports].

linecount_report#
Type

string

Causes mypy to generate a text file report documenting the functions and lines that are typed and untyped within your codebase.

linecoverage_report#
Type

string

Causes mypy to generate a JSON file that maps each source file’s absolute filename to a list of line numbers that belong to typed functions in that file.

lineprecision_report#
Type

string

Causes mypy to generate a flat text file report with per-module statistics of how many lines are typechecked etc.

txt_report / xslt_txt_report#
Type

string

Causes mypy to generate a text file type checking coverage report.

To generate this report, you must either manually install the lxml library or specify mypy installation with the setuptools extra mypy[reports].

xml_report#
Type

string

Causes mypy to generate an XML type checking coverage report.

To generate this report, you must either manually install the lxml library or specify mypy installation with the setuptools extra mypy[reports].

Miscellaneous#

These options may only be set in the global section ([mypy]).

junit_xml#
Type

string

Causes mypy to generate a JUnit XML test result document with type checking results. This can make it easier to integrate mypy with continuous integration (CI) tools.

scripts_are_modules#
Type

boolean

Default

False

Makes script x become module x instead of __main__. This is useful when checking multiple scripts in a single run.

warn_unused_configs#
Type

boolean

Default

False

Warns about per-module sections in the config file that do not match any files processed when invoking mypy. (This requires turning off incremental mode using incremental = False.)

verbosity#
Type

integer

Default

0

Controls how much debug output will be generated. Higher numbers are more verbose.

Using a pyproject.toml file#

Instead of using a mypy.ini file, a pyproject.toml file (as specified by PEP 518) may be used instead. A few notes on doing so:

  • The [mypy] section should have tool. prepended to its name:

    • I.e., [mypy] would become [tool.mypy]

  • The module specific sections should be moved into [[tool.mypy.overrides]] sections:

    • For example, [mypy-packagename] would become:

[[tool.mypy.overrides]]
module = 'packagename'
...
  • Multi-module specific sections can be moved into a single [[tool.mypy.overrides]] section with a module property set to an array of modules:

    • For example, [mypy-packagename,packagename2] would become:

[[tool.mypy.overrides]]
module = [
    'packagename',
    'packagename2'
]
...
  • The following care should be given to values in the pyproject.toml files as compared to ini files:

    • Strings must be wrapped in double quotes, or single quotes if the string contains special characters

    • Boolean values should be all lower case

Please see the TOML Documentation for more details and information on what is allowed in a toml file. See PEP 518 for more information on the layout and structure of the pyproject.toml file.

Example pyproject.toml#

Here is an example of a pyproject.toml file. To use this config file, place it at the root of your repo (or append it to the end of an existing pyproject.toml file) and run mypy.

# mypy global options:

[tool.mypy]
python_version = "2.7"
warn_return_any = true
warn_unused_configs = true
exclude = [
    '^file1\.py$',  # TOML literal string (single-quotes, no escaping necessary)
    "^file2\\.py$",  # TOML basic string (double-quotes, backslash and other characters need escaping)
]

# mypy per-module options:

[[tool.mypy.overrides]]
module = "mycode.foo.*"
disallow_untyped_defs = true

[[tool.mypy.overrides]]
module = "mycode.bar"
warn_return_any = false

[[tool.mypy.overrides]]
module = [
    "somelibrary",
    "some_other_library"
]
ignore_missing_imports = true