Release history

Version 3.9

  • New options flit build --use-vcs and flit build --no-use-vcs to enable & disable including all committed files in the sdist. For now --use-vcs is the default, but this is likely to change in a future version, to bring flit build in line with standard build frontends like python -m build (PR #625).

  • Sdist file names, and the name of the top-level folder in an sdist, are now normalised, in accordance with PEP 625 (PR #628).

  • A statically defined version number can now be parsed from files called, or inside a package, as well as from, so executing code is required in fewer cases (PR #630).

  • Fix setting the flag for regular files in zip metadata (PR #639).

  • The timestamp embedded in the gzip wrapper for sdists now defaults to a fixed date, so building an sdist twice on the same machine should produce identical results, even without any special steps (PR #635). Setting SOURCE_DATE_EPOCH is still recommended for properly reproducible builds.

Version 3.8

  • A project name containing hyphens is now automatically translated to use underscores for the import name (PR #566).

  • New option flit install --only-deps to install the dependencies of the package, but not the package itself.

  • Add support for recursive globbing (**) in sdist includes and excludes (PR #550).

  • Python’s bytecode cache files (__pycache__ folders and .pyc files) are now always excluded from sdists (PR #581).

  • Use tomllib in Python 3.11, rather than tomli (PR #573, PR #604).

  • Fix crash when unable to get a password from keyring (PR #567).

  • Fix including modified files in sdist when using Mercurial (PR #541).

  • Fix for some cases of determining whether a package supports Python 2 or not (PR #593).

  • Fix parsing version number from code using multiple assignments (PR #474).

  • Document how to use a PyPI token with FLIT_PASSWORD (PR #602).

  • Fix link to information about environment variables for pip (PR #576).

  • Link to the docs for the latest stable version in package metadata (PR #589).

  • Remove a mention of the toml package, which is no longer needed, from the Developing Flit page (PR #601).

  • The bootstrap install script for flit_core accepts a new --install-root option.

  • Ensure the license file is included in packages on PyPI (PR #603).

Version 3.7.1

  • Fix building packages which need execution to get the version number, and have a relative import in (PR #531).

Version 3.7

  • Support for external data files such as man pages or Jupyter extension support files (PR #510).

  • Project names are now lowercase in wheel filenames and .dist-info folder names, in line with the specifications (PR #498).

  • Improved support for bootstrapping a Python environment, e.g. for downstream packagers (PR #511). flit_core.wheel is usable with python -m to create wheels before the build tool is available, and flit_core sdists also include a script to install itself from a wheel before installer is available.

  • Use newer importlib APIs, fixing some deprecation warnings (PR #499).

Version 3.6

  • flit_core now bundles the tomli TOML parser library (version 1.2.3) to avoid a circular dependency between flit_core and tomli (PR #492). This means flit_core now has no dependencies except Python itself, both at build time and at runtime, simplifying bootstrapping.

Version 3.5.1

  • Fix development installs with flit install --symlink and --pth-file, which were broken in 3.5.0, especially for packages using a src folder (PR #472).

Version 3.5

  • You can now use Flit to distribute a module or package inside a namespace package (as defined by PEP 420). To do this, specify the import name of the concrete, inner module you are packaging - e.g. name = "" - either in the [project] table, or under [tool.flit.module] if you want to use a different name on PyPI (PR #468).

  • Flit no longer generates a file in sdists (.tar.gz packages) by default (PR #462). Modern packaging tools don’t need this. You can use the --setup-py flag to keep adding it for now, but this will probably be removed at some point in the future.

  • Fixed how flit init handles authors’ names with non-ASCII characters (PR #460).

  • When flit init generates a LICENSE file, the new pyproject.toml now references it (PR #467).

Version 3.4

  • Python 3.6 or above is now required, both for flit and flit_core.

  • Add a --setup-py option to flit build and flit publish, and a warning when neither this nor --no-setup-py are specified (PR #431). A future version will stop generating files in sdists by default.

  • Add support for standardised editable installs - pip install -e - according to PEP 660 (PR #400).

  • Add a --pypirc option for flit publish to specify an alternative path to a .pypirc config file describing package indexes (PR #434).

  • Fix installing dependencies specified in a [project] table (PR #433).

  • Fix building wheels when SOURCE_DATE_EPOCH (see Reproducible builds) is set to a date before 1980 (PR #448).

  • Switch to using the tomli TOML parser, in common with other packaging projects (PR #438). This supports TOML version 1.0.

  • Add a document on Bootstrapping (PR #441).

Version 3.3

  • PKG-INFO files in sdists are now generated the same way as METADATA in wheels, fixing some issues with sdists (PR #410).

  • flit publish now sends SHA-256 hashes, fixing uploads to GitLab package repositories (PR #416).

  • The [project] metadata table from PEP 621 is now fully supported and documented. Projects using this can now specify requires = ["flit_core >=3.2,<4"] in the [build-system] table.

Version 3.2

  • Experimental support for specifying metadata in a [project] table in pyproject.toml as specified by PEP 621 (PR #393). If you try using this, please specify requires = ["flit_core >=3.2.0,<3.3"] in the [build-system] table for now, in case it needs to change for the next release.

  • Fix writing METADATA file with multi-line information in certain fields such as Author (PR #402).

  • Fix building wheel when a directory such as LICENSES appears in the project root directory (PR #401).

Version 3.1

  • Update handling of names & version numbers in wheel filenames and .dist-info folders in line with changes in the specs (PR #395).

  • Switch from the deprecated pytoml package to toml (PR #378).

  • Fix specifying backend-path in pyproject.toml for flit-core (as a list instead of a string).

Version 3.0

Breaking changes:

  • Projects must now provide Flit with information in pyproject.toml files, not the older flit.ini format (PR #338).

  • flit_core once again requires Python 3 (>=3.4). Packages that support Python 2 can still be built by flit_core 2.x, but can’t rely on new features (PR #342).

  • The deprecated flit installfrom command was removed (PR #334). You can use pip install git+ instead.

Features and fixes:

  • Fix building sdists from a git repository with non-ASCII characters in filenames (PR #346).

  • Fix identifying the version number when the code contains a subscript assignment before __version__ = (PR #348).

  • Script entry points can now use a class method (PR #359).

  • Set suitable permission bits on metadata files in wheels (PR #256).

  • Fixed line endings in the RECORD file when installing on Windows (PR #368).

  • Support for recording the source of local installations, as in PEP 610 (PR #335).

  • flit init will check for a README in the root of the project and automatically set it as description-file (PR #337).

  • Pygments is not required for checking reStructuredText READMEs (PR #357).

  • Packages where the version number can be recognised without executing their code don’t need their dependencies installed to build, which should make them build faster (PR #361).

  • Ensure the installed RECORD file is predictably ordered (PR #366).

Version 2.3

  • New projects created with flit init now declare that they require flit_core >=2,<4 (PR #328). Any projects using pyproject.toml (not flit.ini) should be compatible with flit 3.x.

  • Fix selecting files from a git submodule to include in an sdist (PR #324).

  • Fix checking classifiers when no writeable cache directory is available (PR #319).

  • Better errors when trying to install to a mis-spelled or missing Python interpreter (PR #331).

  • Fix specifying --repository before upload (PR #322). Passing the option like this is deprecated, and you should now pass it after upload.

  • Documentation improvements (PR #327, PR #318, PR #314)

Version 2.2

  • Allow underscores in package names with Python 2 (PR #305).

  • Add a --no-setup-py option to build sdists without a backwards-compatible file (PR #311).

  • Fix the generated file for packages using a src/ layout (PR #303).

  • Fix detecting when more than one file matches the module name specified (PR #307).

  • Fix installing to a venv on Windows with the --python option (PR #300).

  • Don’t echo the command in scripts installed with --symlink or --pth-file on Windows (PR #310).

  • New script to set up a development installation of Flit from the repository (PR #301, PR #306).

Version 2.1

  • Use compression when adding files to wheels.

  • Added the FLIT_INSTALL_PYTHON environment variable (PR #295), to configure flit to always install into a Python other than the one it’s running on.

  • flit_core uses the intreehooks shim package to load its bootstrapping backend, until a released version of pip supports the standard backend-path mechanism.

Version 2.0

Flit 2 is a major architecture change. The flit_core package now provides a PEP 517 backend for building packages, while flit is a command line interface extending that.

The build backend works on Python 2, so tools like pip should be able to install packages built with flit from source on Python 2. The flit command requires Python 3.5 or above. You will need to change the build-system table in your pyproject.toml file to look like this:

requires = ["flit_core >=2,<4"]
build-backend = "flit_core.buildapi"

Other changes include:

  • Support for storing your code under a src/ folder (PR #260). You don’t need to change any configuration if you do this.

  • Options to control what files are included in an sdist - see Sdist section for the details.

  • Requirements can specify a URL ‘direct reference’, as an alternative to a version number, with the syntax defined in PEP 440: requests @

  • Fix the shebang of scripts installed with the --python option and the --symlink flag (PR #286).

  • Installing with --deps develop now installs normal dependencies as well as development dependencies.

  • Author email is no longer required in the metadata table (PR #289).

  • More error messages are now shown without a traceback (PR #254)

Version 1.3

  • Fix for building sdists from a subdirectory in a Mercurial repository (PR #233).

  • Fix for getting the docstring and version from modules defining their encoding (PR #239).

  • Fix for installing packages with flit installfrom (PR #221).

  • Packages with requirements no longer get a spurious Provides-Extra: .none metadata entry (#228).

  • Better check of whether python-requires includes any Python 2 version (PR #232).

  • Better check of home page URLs in flit init (PR #230).

  • Better error message when the description file is not found (PR #234).

  • Updated a help message to refer to pyproject.toml (PR #240).

  • Improve tests of flit init (PR #229).

Version 1.2.1

  • Fix for installing packages with flit install.

  • Make requests_download an extra dependency, to avoid a circular build dependency. To use flit installfrom, you can install with pip install flit[installfrom]. Note that the installfrom subcommand is deprecated, as it will soon be possible to use pip to install Flit projects directly from a VCS URL.

Version 1.2

  • Fixes for packages specifying requires-extra: sdists should now work, and environment markers can be used together with requires-extra.

  • Fix running flit installfrom without a config file present in the working directory.

  • The error message for a missing or empty docstring tells you what file the docstring should be in.

  • Improvements to documentation on version selectors for requirements.

Version 1.1

  • Packages can now have ‘extras’, specified as requires-extra in the pyproject.toml file. These are additional dependencies for optional features.

  • The home-page metadata field is no longer required.

  • Additional project URLs are now validated.

  • flit -V is now equivalent to flit --version.

  • Various improvements to documentation.

Version 1.0

  • The description file may now be written in reStructuredText, Markdown or plain text. The file extension should indicate which of these formats it is (.rst, .md or .txt). Previously, only reStructuredText was officially supported.

  • Multiple links (e.g. documentation, bug tracker) can now be specified in a new [tool.flit.metadata.urls] section of pyproject.toml.

  • Dependencies are now correctly installed to the target Python when you use the --symlink or --pth-file options.

  • Dependencies are only installed to the Python where Flit is running if it fails to get the docstring and version number without them.

  • The commands deprecated in 0.13—flit wheel, flit sdist and flit register—have been removed.

Although version 1.0 sounds like a milestone, there’s nothing that makes this release especially significant. It doesn’t represent a step change in stability or completeness. Flit has been gradually maturing for some time, and I chose this point to end the series of 0.x version numbers.

Version 0.13

  • Better validation of several metadata fields (dist-name, requires, requires-python, home-page), and of the version number.

  • New FLIT_ALLOW_INVALID environment variable to ignore validation failures in case they go wrong.

  • The list of valid classifiers is now fetched from Warehouse (, rather than the older site.

  • Deprecated flit wheel and flit sdist subcommands: use flit build.

  • Deprecated flit register: you can no longer register a package separately from uploading it.

Version 0.12.3

  • Fix building and installing packages with a - in the distribution name.

  • Fix numbering in README.

Version 0.12.2

  • New tool to convert flit.ini to pyproject.toml:

    python3 -m flit.tomlify
  • Use the PAX tar format for sdists, as specified by PEP 517.

Version 0.12.1

  • Restore dependency on zipfile36 backport package.

  • Add some missing options to documentation of flit install subcommand.

  • Rearrange environment variables in the docs.

Version 0.12

  • Switch the config to pyproject.toml by default instead of flit.ini, and implement the PEP 517 API.

  • A new option --pth-file allows for development installation on Windows (where --symlink usually won’t work).

  • Normalise file permissions in the zip file, making builds more reproducible across different systems.

  • Sdists (.tar.gz packages) can now also be reproducibly built by setting SOURCE_DATE_EPOCH.

  • For most modules, Flit can now extract the version number and docstring without importing it. It will still fall back to importing where getting these from the AST fails.

  • flit build will build the wheel from the sdist, helping to ensure that files aren’t left out of the sdist.

  • All list fields in the INI file now ignore blank lines (requires, dev-requires, classifiers).

  • Fix the path separator in the RECORD file of a wheel built on Windows.

  • Some minor fixes to building reproducible wheels.

  • If building a wheel fails, the temporary file created will be cleaned up.

  • Various improvements to docs and README.

Version 0.11.4

  • Explicitly open various files as UTF-8, rather than relying on locale encoding.

  • Link to docs from README.

  • Better test coverage, and a few minor fixes for problems revealed by tests.

Version 0.11.3

  • Fixed a bug causing failed uploads when the password is entered in the terminal.

Version 0.11.2

  • A couple of behaviour changes when uploading to warehouse.

Version 0.11.1

  • Fixed a bug when you use flit to build an sdist from a subdirectory inside a VCS checkout. The VCS is now correctly detected.

  • Fix the rst checker for newer versions of docutils, by upgrading the bundled copy of readme_renderer.

Version 0.11

  • Flit can now build sdists (tarballs) and upload them to PyPI, if your code is in a git or mercurial repository. There are new commands:

    • flit build builds both a wheel and an sdist.

    • flit publish builds and uploads a wheel and an sdist.

  • Smarter ways of getting the information needed for upload:

    • If you have the keyring package installed, flit can use it to store your password, rather than keeping it in plain text in ~/.pypirc.

    • If ~/.pypirc does not already exist, and you are prompted for your username, flit will write it into that file.

    • You can provide the information as environment variables: FLIT_USERNAME, FLIT_PASSWORD and FLIT_INDEX_URL. Use this to upload packages from a CI service, for instance.

  • Include ‘LICENSE’ or ‘COPYING’ files in wheels.

  • Fix for flit install --symlink inside a virtualenv.

Version 0.10

  • Downstream packagers can use the FLIT_NO_NETWORK environment variable to stop flit downloading data from the network.

Version 0.9

  • flit install and flit installfrom now take an optional --python argument, with the path to the Python executable you want to install it for. Using this, you can install modules to Python 2.

  • Installing a module normally (without --symlink) builds a wheel and uses pip to install it, which should work better in some corner cases.

Version 0.8

  • A new flit installfrom subcommand to install a project from a source archive, such as from Github.

  • Reproducible builds - you can produce byte-for-byte identical wheels.

  • A warning for non-canonical version numbers according to PEP 440.

  • Fix for installing projects on Windows.

  • Better error message when module docstring is only whitespace.

Version 0.7

  • A new dev-requires field in the config file for development requirements, used when doing flit install.

  • Added a --deps option for flit install to control which dependencies are installed.

  • Flit can now be invoked with python -m flit.

Version 0.6

  • flit install now ensures requirements specified in flit.ini are installed, using pip.

  • If you specify a description file, flit now warns you if it’s not valid reStructuredText (since invalid reStructuredText is treated as plain text on PyPI).

  • Improved the error message for mis-spelled keys in flit.ini.

Version 0.5

  • A new flit init command to quickly define the essential basic metadata for a package.

  • Support for entry points.

  • A new flit register command to register a package without uploading it, for when you want to claim a name before you’re ready to release.

  • Added a --repository option for specifying an alternative PyPI instance.

  • Added a --debug flag to show debug-level log messages.

  • Better error messages when the module docstring or __version__ is missing.

Version 0.4

  • Users can now specify dist-name in the config file if they need to use different names on PyPI and for imports.

  • Classifiers are now checked against a locally cached list of valid classifiers.

  • Packages can be locally installed into environments for development.

  • Local installation now creates a PEP 376 .dist-info folder instead of .egg-info.