Flit command line interface

All operations use the flit command, followed by one of a number of subcommands.

Common options

-f <path>, --ini-file <path>

Path to a config file specifying the module to build. The default is pyproject.toml or flit.ini

--repository <repository>

Name of a repository to upload packages to. Should match a section in ~/.pypirc. The default is pypi. See Controlling package uploads.


Show the version of Flit in use.


Show help on the command-line interface.


Show more detailed logs about what flit is doing.

flit build

Build a wheel and an sdist (tarball) from the package.

--format <format>

Limit to building either wheel or sdist.

flit publish

Build a wheel and an sdist (tarball) from the package, and upload them to PyPI or another repository.

--format <format>

Limit to publishing either wheel or sdist. You should normally publish the two formats together.

flit install

Install the package on your system.

-s, --symlink

Symlink the module into site-packages rather than copying it, so that you can test changes without reinstalling the module.


Create a .pth file in site-packages rather than copying the module, so you can test changes without reinstalling. This is a less elegant alternative to --symlink, but it works on Windows, which typically doesn’t allow symlinks.

--deps <dependency option>

Which dependencies to install. One of all, production, develop, or none. all and develop install the extras test, doc, and dev. Default all.

--extras <extra[,extra,...]>

Which named extra features to install dependencies for. Specify all to install all optional dependencies, or a comma-separated list of extras. Default depends on --deps.


Do a user-local installation. This is the default if flit is not in a virtualenv or conda env (if the environment’s library directory is read-only and site.ENABLE_USER_SITE is true).


Install into the environment. This is the default in a virtualenv or conda env (if the environment’s library directory is writable or site.ENABLE_USER_SITE is false).

--python <path to python>

Install for another Python, identified by the path of the python executable. The default is to install the module for the copy of Python that is running Flit. Using this option, you can install a module for Python 2, for instance.


Flit calls pip to do the installation. You can set any of pip’s options using its environment variables.

When you use the --symlink or --pth-file options, pip is used to install dependencies. Otherwise, Flit builds a wheel and then calls pip to install that.

flit init

Create a new pyproject.toml config file by prompting for information about the module in the current directory.

Environment variables


New in version 0.10.

Setting this to any non-empty value will stop flit from making network connections (unless you explicitly ask to upload a package). This is intended for downstream packagers, so if you use this, it’s up to you to ensure any necessary dependencies are installed.


By default, flit install will fail when run as root on POSIX systems, because installing Python modules systemwide is not recommended. Setting this to any non-empty value allows installation as root. It has no effect on Windows.


New in version 0.11.

Set a username, password, and index URL for uploading packages. See uploading packages with environment variables for more information.


New in version 0.13.

Setting this to any non-empty value tells Flit to continue if it detects invalid metadata, instead of failing with an error. Problems will still be reported in the logs, but won’t cause Flit to stop.

If the metadata is invalid, uploading the package to PyPI may fail. This environment variable provides an escape hatch in case Flit incorrectly rejects your valid metadata. If you need to use it and you believe your metadata is valid, please open an issue.


To make reproducible builds, set this to a timestamp as a number of seconds since the start of the year 1970 in UTC, and document the value you used. On Unix systems, you can get a value for the current time by running:

date +%s