Invoking Flake8

Once you have installed Flake8, you can begin using it. Most of the time, you will be able to generically invoke Flake8 like so:

flake8 ...

Where you simply allow the shell running in your terminal to locate Flake8. In some cases, though, you may have installed Flake8 for multiple versions of Python (e.g., Python 2.7 and Python 3.5) and you need to call a specific version. In that case, you will have much better results using:

python2.7 -m flake8


python3.5 -m flake8

Since that will tell the correct version of Python to run Flake8.


Installing Flake8 once will not install it on both Python 2.7 and Python 3.5. It will only install it for the version of Python that is running pip.

It is also possible to specify command-line options directly to Flake8:

flake8 --select E123


python<version> -m flake8 --select E123


This is the last time we will show both versions of an invocation. From now on, we’ll simply use flake8 and assume that the user knows they can instead use python<version> -m flake8 instead.

It’s also possible to narrow what Flake8 will try to check by specifying exactly the paths and directories you want it to check. Let’s assume that we have a directory with python files and sub-directories which have python files (and may have more sub-directories) called my_project. Then if we only want errors from files found inside my_project we can do:

flake8 my_project

And if we only want certain errors (e.g., E123) from files in that directory we can also do:

flake8 --select E123 my_project

If you want to explore more options that can be passed on the command-line, you can use the --help option:

flake8 --help

And you should see something like:

Usage: flake8 [options] file file ...

  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -v, --verbose         Print more information about what is happening in
                        flake8. This option is repeatable and will increase
                        verbosity each time it is repeated.
  -q, --quiet           Report only file names, or nothing. This option is
  --count               Print total number of errors and warnings to standard
                        error and set the exit code to 1 if total is not
  --diff                Report changes only within line number ranges in the
                        unified diff provided on standard in by the user.
  --exclude=patterns    Comma-separated list of files or directories to
  --filename=patterns   Only check for filenames matching the patterns in this
                        comma-separated list. (Default: *.py)
  --format=format       Format errors according to the chosen formatter.
  --hang-closing        Hang closing bracket instead of matching indentation
                        of opening bracket's line.
  --ignore=errors       Comma-separated list of errors and warnings to ignore
                        (or skip). For example, ``--ignore=E4,E51,W234``.
                        (Default: E121,E123,E126,E226,E24,E704)
  --max-line-length=n   Maximum allowed line length for the entirety of this
                        run. (Default: 79)
  --select=errors       Comma-separated list of errors and warnings to enable.
                        For example, ``--select=E4,E51,W234``. (Default: )
  --disable-noqa        Disable the effect of "# noqa". This will report
                        errors on lines with "# noqa" at the end.
  --show-source         Show the source generate each error or warning.
  --statistics          Count errors and warnings.
                        Enable plugins and extensions that are otherwise
                        disabled by default
  --exit-zero           Exit with status code "0" even if there are errors.
  -j JOBS, --jobs=JOBS  Number of subprocesses to use to run checks in
                        parallel. This is ignored on Windows. The default,
                        "auto", will auto-detect the number of processors
                        available to use. (Default: auto)
                        Redirect report to a file.
  --tee                 Write to stdout and output-file.
                        Provide extra config files to parse in addition to the
                        files found by Flake8 by default. These files are the
                        last ones read and so they take the highest precedence
                        when multiple files provide the same option.
  --config=CONFIG       Path to the config file that will be the authoritative
                        config source. This will cause Flake8 to ignore all
                        other configuration files.
  --isolated            Ignore all found configuration files.
  --builtins=BUILTINS   define more built-ins, comma separated
  --doctests            check syntax of the doctests
                        Run doctests only on these files
                        Skip these files when running doctests

Installed plugins: pyflakes: 1.0.0, pep8: 1.7.0