# CLI Reference ## ty An extremely fast Python type checker.

Usage

``` ty ```

Commands

ty check: Check a project for type errors
ty server: Start the language server
ty version: Display ty's version
ty help: Print this message or the help of the given subcommand(s)

## ty check Check a project for type errors

Usage

``` ty check [OPTIONS] [PATH]... ```

Arguments

PATHS: List of files or directories to check [default: the project root]

Options

--color when

Control when colored output is used

Possible values:

auto: Display colors if the output goes to an interactive terminal
always: Always display colors
never: Never display colors

--config, -c config-option

A TOML <KEY> = <VALUE> pair (such as you might find in a ty.toml configuration file) overriding a specific configuration option.

Overrides of individual settings using this option always take precedence over all configuration files.

--config-file path

The path to a ty.toml file to use for configuration.

While ty configuration can be included in a pyproject.toml file, it is not allowed in this context.

May also be set with the TY_CONFIG_FILE environment variable.

--error rule

Treat the given rule as having severity 'error'. Can be specified multiple times.

--error-on-warning

Use exit code 1 if there are any warning-level diagnostics

--exclude exclude

Glob patterns for files to exclude from type checking.

Uses gitignore-style syntax to exclude files and directories from type checking. Supports patterns like tests/, *.tmp, **/__pycache__/**.

--exit-zero

Always use exit code 0, even when there are error-level diagnostics

--extra-search-path path

Additional path to use as a module-resolution source (can be passed multiple times)

--help, -h

Print help (see a summary with '-h')

--ignore rule

Disables the rule. Can be specified multiple times.

--output-format output-format

The format to use for printing diagnostic messages

Possible values:

full: Print diagnostics verbosely, with context and helpful hints [default]
concise: Print diagnostics concisely, one per line

--project project

Run the command within the given project directory.

All pyproject.toml files will be discovered by walking up the directory tree from the given project directory, as will the project's virtual environment (.venv) unless the venv-path option is set.

Other command-line arguments (such as relative paths) will be resolved relative to the current working directory.

--python path

Path to the Python environment.

ty uses the Python environment to resolve type information and third-party dependencies.

If not specified, ty will attempt to infer it from the VIRTUAL_ENV or CONDA_PREFIX environment variables, or discover a .venv directory in the project root or working directory.

If a path to a Python interpreter is provided, e.g., .venv/bin/python3, ty will attempt to find an environment two directories up from the interpreter's path, e.g., .venv. At this time, ty does not invoke the interpreter to determine the location of the environment. This means that ty will not resolve dynamic executables such as a shim.

ty will search in the resolved environment's site-packages directories for type information and third-party imports.

--python-platform, --platform platform

Target platform to assume when resolving types.

This is used to specialize the type of sys.platform and will affect the visibility of platform-specific functions and attributes. If the value is set to all, no assumptions are made about the target platform. If unspecified, the current system's platform will be used.

--python-version, --target-version version

Python version to assume when resolving types.

The Python version affects allowed syntax, type definitions of the standard library, and type definitions of first- and third-party modules that are conditional on the Python version.

If a version is not specified on the command line or in a configuration file, ty will try the following techniques in order of preference to determine a value: 1. Check for the project.requires-python setting in a pyproject.toml file and use the minimum version from the specified range 2. Check for an activated or configured Python environment and attempt to infer the Python version of that environment 3. Fall back to the latest stable Python version supported by ty (currently Python 3.13)

Possible values: