Command Line Interface

The command line interface of Flake8 is modeled as an application via Application. When a user runs flake8 at their command line, main() is run which handles management of the application.

User input is parsed twice to accommodate logging and verbosity options passed by the user as early as possible. This is so as much logging can be produced as possible.

The default Flake8 options are registered by register_default_options(). Trying to register these options in plugins will result in errors.

API Documentation

flake8.main.cli.main(argv=None)

Execute the main bit of the application.

This handles the creation of an instance of Application, runs it, and then exits the application.

Parameters:

argv (Sequence[str] | None) – The arguments to be passed to the application for parsing.

Return type:

int

class flake8.main.application.Application

Abstract our application into a class.

catastrophic_failure

Whether or not something catastrophic happened and we should exit with a non-zero status code

end_time: float | None

The timestamp when the Application finished reported errors.

exit_code()

Return the program exit code.

Return type:

int

file_checker_manager: Manager | None

The flake8.checker.Manager that will handle running all of the checks selected by the user.

find_plugins(cfg, cfg_dir, *, enable_extensions, require_plugins)

Find and load the plugins for this application.

Set plugins based on loaded plugins.

Parameters:

• cfg (RawConfigParser) –

• cfg_dir (str) –

• enable_extensions (str | None) –

• require_plugins (str | None) –

Return type:

None

formatter: BaseFormatter | None

The user-selected formatter from formatting_plugins

guide: StyleGuideManager | None

The flake8.style_guide.StyleGuideManager built from the user’s options

initialize(argv)

Initialize the application to be run.

This finds the plugins, registers their options, and parses the command-line arguments.

Parameters:

argv (Sequence[str]) –

Return type:

None

make_file_checker_manager()

Initialize our FileChecker Manager.

Return type:

None

make_formatter()

Initialize a formatter based on the parsed options.

Return type:

None

make_guide()

Initialize our StyleGuide.

Return type:

None

option_manager: OptionManager | None

The instance of flake8.options.manager.OptionManager used to parse and handle the options and arguments passed by the user

options: Namespace | None

The user-supplied options parsed into an instance of argparse.Namespace

parse_configuration_and_cli(cfg, cfg_dir, argv)

Parse configuration files and the CLI options.

Parameters:

• cfg (RawConfigParser) –

• cfg_dir (str) –

• argv (List[str]) –

Return type:

None

parse_preliminary_options(argv)

Get preliminary options from the CLI, pre-plugin-loading.

We need to know the values of a few standard options so that we can locate configuration files and configure logging.

Since plugins aren’t loaded yet, there may be some as-yet-unknown options; we ignore those for now, they’ll be parsed later when we do real option parsing.

Parameters:

argv (Sequence[str]) – Command-line arguments passed in directly.

Returns:

Populated namespace and list of remaining argument strings.

Return type:

Tuple[Namespace, List[str]]

parsed_diff: Dict[str, Set[int]]

The parsed diff information

prelim_arg_parser

The prelimary argument parser for handling options required for obtaining and parsing the configuration file.

register_plugin_options()

Register options provided by plugins to our option manager.

Return type:

None

report()

Report errors, statistics, and benchmarks.

Return type:

None

report_benchmarks()

Aggregate, calculate, and report benchmarks for this run.

Return type:

None

report_errors()

Report all the errors found by flake8 3.0.

This also updates the result_count attribute with the total number of errors, warnings, and other messages found.

Return type:

None

report_statistics()

Aggregate and report statistics from this run.

Return type:

None

result_count

The number of errors, warnings, and other messages after running flake8 and taking into account ignored errors and lines.

run(argv)

Run our application.

This method will also handle KeyboardInterrupt exceptions for the entirety of the flake8 application. If it sees a KeyboardInterrupt it will forcibly clean up the Manager.

Parameters:

argv (Sequence[str]) –

Return type:

None

run_checks()

Run the actual checks with the FileChecker Manager.

This method encapsulates the logic to make a Manger instance run the checks it is managing.

Return type:

None

start_time

The timestamp when the Application instance was instantiated.

total_result_count

The total number of errors before accounting for ignored errors and lines.

flake8.main.options.register_default_options(option_manager)

Register the default options on our OptionManager.

The default options include:

• -q/--quiet

• --color

• --count

• --diff

• --exclude

• --extend-exclude

• --filename

• --format

• --hang-closing

• --ignore

• --extend-ignore

• --per-file-ignores

• --max-line-length

• --max-doc-length

• --indent-size

• --select

• --extend-select

• --disable-noqa

• --show-source

• --statistics

• --exit-zero

• -j/--jobs

• --tee

• --benchmark

• --bug-report

Parameters:

option_manager (OptionManager) –

Return type:

None