Mypy can optionally display an error code such as
after each error message. Error codes serve two purposes:
It’s possible to silence specific error codes on a line using
# type: ignore[code]. This way you won’t accidentally ignore other, potentially more serious errors.
The error code can be used to find documentation about the error. The next two topics (Error codes enabled by default and Error codes for optional checks) document the various error codes mypy can report.
Most error codes are shared between multiple related error messages. Error codes may change in future mypy releases.
Displaying error codes#
Error codes are displayed by default. Use
hide_error_codes = True to hide error codes. Error codes are shown inside square brackets:
$ mypy prog.py prog.py:1: error: "str" has no attribute "trim" [attr-defined]
It’s also possible to require error codes for
type: ignore comments.
See ignore-without-code for more information.
Silencing errors based on error codes#
You can use a special comment
# type: ignore[code, ...] to only
ignore errors with a specific error code (or codes) on a particular
line. This can be used even if you have not configured mypy to show
error codes. Currently it’s only possible to disable arbitrary error
codes on individual lines using this comment.
You can also use
to disable specific error codes globally.
This example shows how to ignore an error about an imported name mypy thinks is undefined:
# 'foo' is defined in 'foolib', even though mypy can't see the # definition. from foolib import foo # type: ignore[attr-defined]
Enabling specific error codes#
There are command-line flags and config file settings for enabling
certain optional error codes, such as
which enables the
no-untyped-def error code.
You can use
enable specific error codes that don’t have a dedicated command-line
flag or config file setting.
Per-module enabling/disabling error codes#
You can use configuration file sections to enable or
disable specific error codes only in some modules. For example, this
config will enable non-annotated empty containers in tests, while keeping
other parts of code checked in strict mode:
[mypy] strict = True [mypy-tests.*] allow_untyped_defs = True allow_untyped_calls = True disable_error_code = var-annotated, has-type
Note that per-module enabling/disabling acts as override over the global options. So that you don’t need to repeat the error code lists for each module if you have them in global config section. For example:
[mypy] enable_error_code = truthy-bool, ignore-without-code, unused-awaitable [mypy-extensions.*] disable_error_code = unused-awaitable
The above config will allow unused awaitables in extension modules, but will still keep the other two error codes enabled. The overall logic is following:
Command line and/or config main section set global error codes
Individual config sections adjust them per glob/module
# mypy: ...comments can further adjust them for a specific module
So one can e.g. enable some code globally, disable it for all tests in the corresponding config section, and then re-enable it with an inline comment in some specific test.
Subcodes of error codes#
In some cases, mostly for backwards compatibility reasons, an error
code may be covered also by another, wider error code. For example, an error with
[method-assign] can be ignored by
# type: ignore[assignment].
Similar logic works for disabling error codes globally. If a given error code
is a subcode of another one, it will be mentioned in the documentation for the narrower
code. This hierarchy is not nested: there cannot be subcodes of other