The pyproject.toml config file

This file lives next to the module or package.

Note

Older version of Flit (up to 0.11) used a flit.ini file for similar information. These files no longer work with Flit 3 and above.

Run python3 -m flit.tomlify to convert a flit.ini file to pyproject.toml.

Build system section

This tells tools like pip to build your project with flit. It’s a standard defined by PEP 517. For any new project using Flit, it will look like this:

[build-system]
requires = ["flit_core >=3.2,<4"]
build-backend = "flit_core.buildapi"

Version constraints:

  • For now, all packages should specify <4, so they won’t be impacted by changes in the next major version.

  • New style metadata requires flit_core >=3.2

  • Old style metadata requires flit_core >=2,<4

  • The older flit.ini file requires flit_core <3.

  • TOML features new in version 1.0 require flit_core >=3.4.

  • flit_core 3.3 is the last version supporting Python 3.4 & 3.5. Packages supporting these Python versions can only use TOML v0.5.

  • Only flit_core 2.x can build packages on Python 2, so packages still supporting Python 2 cannot use new-style metadata (the [project] table).

New style metadata

New in version 3.2.

The new standard way to specify project metadata is in a [project] table, as defined by PEP 621. Flit works for now with either this or the older [tool.flit.metadata] table (described below), but it won’t allow you to mix them.

A simple [project] table might look like this:

[project]
name = "astcheck"
authors = [
    {name = "Thomas Kluyver", email = "thomas@kluyver.me.uk"},
]
readme = "README.rst"
classifiers = [
    "License :: OSI Approved :: MIT License",
]
requires-python = ">=3.5"
dynamic = ["version", "description"]

The allowed fields are:

name

The name your package will have on PyPI. This field is required. For Flit, this also points to your package as an import name by default (see Module section if that needs to be different).

version

Version number as a string. If you want Flit to get this from a __version__ attribute, leave it out of the TOML config and include “version” in the dynamic field.

description

A one-line description of your project. If you want Flit to get this from the module docstring, leave it out of the TOML config and include “description” in the dynamic field.

readme

A path (relative to the .toml file) to a file containing a longer description of your package to show on PyPI. This should be written in reStructuredText, Markdown or plain text, and the filename should have the appropriate extension (.rst, .md or .txt). Alternatively, readme can be a table with either a file key (a relative path) or a text key (literal text), and an optional content-type key (e.g. text/x-rst).

requires-python

A version specifier for the versions of Python this requires, e.g. ~=3.3 or >=3.3,<4, which are equivalents.

license

A table with either a file key (a relative path to a license file) or a text key (the license text).

authors

A list of tables with name and email keys (both optional) describing the authors of the project.

maintainers

Same format as authors.

keywords

A list of words to help with searching for your package.

classifiers

A list of Trove classifiers. Add Private :: Do Not Upload into the list to prevent a private package from being uploaded to PyPI by accident.

dependencies & optional-dependencies

See Dependencies.

urls

See URLs table.

scripts & gui-scripts

See Scripts section.

entry-points

See Entry points sections.

dynamic

A list of field names which aren’t specified here, for which Flit should find a value at build time. Only “version” and “description” are accepted.

Dependencies

The dependencies field is a list of other packages from PyPI that this package needs. Each package may be followed by a version specifier like >=4.1, and/or an environment marker after a semicolon. For example:

dependencies = [
    "requests >=2.6",
    "configparser; python_version == '2.7'",
]

The [project.optional-dependencies] table contains lists of packages needed for every optional feature. The requirements are specified in the same format as for dependencies. For example:

[project.optional-dependencies]
test = [
    "pytest >=2.7.3",
    "pytest-cov",
]
doc = ["sphinx"]

You can call these optional features anything you want, although test and doc are common ones. You specify them for installation in square brackets after the package name or directory, e.g. pip install '.[test]'.

URLs table

Your project’s page on pypi.org can show a number of links. You can point people to documentation or a bug tracker, for example.

This section is called [project.urls] in the file. You can use any names inside it. Here it is for flit:

[project.urls]
Documentation = "https://flit.readthedocs.io/en/latest/"
Source = "https://github.com/pypa/flit"

Scripts section

This section is called [project.scripts] in the file. Each key and value describes a shell command to be installed along with your package. These work like setuptools ‘entry points’. Here’s the section for flit:

[project.scripts]
flit = "flit:main"

This will create a flit command, which will call the function main() imported from flit.

A similar table called [project.gui-scripts] defines commands which launch a GUI. This only makes a difference on Windows, where GUI scripts are run without a console.

Entry points sections

You can declare entry points using sections named [project.entry-points.groupname]. E.g. to provide a pygments lexer from your package:

[project.entry-points."pygments.lexers"]
dogelang = "dogelang.lexer:DogeLexer"

In each package:name value, the part before the colon should be an importable module name, and the latter part should be the name of an object accessible within that module. The details of what object to expose depend on the application you’re extending.

If the group name contains a dot, it must be quoted ("pygments.lexers" above). Script entry points are defined in scripts tables, so you can’t use the group names console_scripts or gui_scripts here.

Module section

If your package will have different names for installation and import, you should specify the install (PyPI) name in the [project] table (see above), and the import name in a [tool.flit.module] table:

[project]
name = "pynsist"
# ...

[tool.flit.module]
name = "nsist"

Old style metadata

Flit’s older way to specify metadata is in a [tool.flit.metadata] table, along with [tool.flit.scripts] and [tool.flit.entrypoints], described below. This is still recognised for now, but you can’t mix it with New style metadata.

There are three required fields:

module

The name of the module/package, as you’d use in an import statement.

author

Your name

author-email

Your email address

e.g. for flit itself

[tool.flit.metadata]
module = "flit"
author = "Thomas Kluyver"
author-email = "thomas@kluyver.me.uk"

Changed in version 1.1: home-page was previously required.

The remaining fields are optional:

home-page

A URL for the project, such as its Github repository.

requires

A list of other packages from PyPI that this package needs. Each package may be followed by a version specifier like (>=4.1) or >=4.1, and/or an environment marker after a semicolon. For example:

requires = [
    "requests >=2.6",
    "configparser; python_version == '2.7'",
]
requires-extra

Lists of packages needed for every optional feature. The requirements are specified in the same format as for requires. The requirements of the two reserved extras test and doc as well as the extra dev are installed by flit install. For example:

[tool.flit.metadata.requires-extra]
test = [
    "pytest >=2.7.3",
    "pytest-cov",
]
doc = ["sphinx"]

New in version 1.1.

description-file

A path (relative to the .toml file) to a file containing a longer description of your package to show on PyPI. This should be written in reStructuredText, Markdown or plain text, and the filename should have the appropriate extension (.rst, .md or .txt).

classifiers

A list of Trove classifiers. Add Private :: Do Not Upload into the list to prevent a private package from uploading on PyPI by accident.

requires-python

A version specifier for the versions of Python this requires, e.g. ~=3.3 or >=3.3,<4 which are equivalents.

dist-name

If you want your package’s name on PyPI to be different from the importable module name, set this to the PyPI name.

keywords

Comma separated list of words to help with searching for your package.

license

The name of a license, if you’re using one for which there isn’t a Trove classifier. It’s recommended to use Trove classifiers instead of this in most cases.

maintainer, maintainer-email

Like author, for if you’ve taken over a project from someone else.

Here was the metadata section from flit using the older style:

[tool.flit.metadata]
module="flit"
author="Thomas Kluyver"
author-email="thomas@kluyver.me.uk"
home-page="https://github.com/pypa/flit"
requires=[
    "flit_core >=2.2.0",
    "requests",
    "docutils",
    "tomli",
    "tomli-w",
]
requires-python=">=3.6"
description-file="README.rst"
classifiers=[
    "Intended Audience :: Developers",
    "License :: OSI Approved :: BSD License",
    "Programming Language :: Python :: 3",
    "Topic :: Software Development :: Libraries :: Python Modules",
]

URLs subsection

Your project’s page on pypi.org can show a number of links, in addition to the home-page URL described above. You can point people to documentation or a bug tracker, for example.

This section is called [tool.flit.metadata.urls] in the file. You can use any names inside it. Here it is for flit:

[tool.flit.metadata.urls]
Documentation = "https://flit.readthedocs.io/en/latest/"

New in version 1.0.

Scripts section

A [tool.flit.scripts] table can be used along with [tool.flit.metadata]. It is in the same format as the newer [project.scripts] table described above.

Entry points sections

[tool.flit.entrypoints] tables can be used along with [tool.flit.metadata]. They are in the same format as the newer [project.entry-points] tables described above.

Sdist section

New in version 2.0.

When you use flit build or flit publish, Flit builds an sdist (source distribution) tarball containing the files that are checked into version control (git or mercurial). If you want more control, or it doesn’t recognise your version control system, you can give lists of paths or glob patterns as include and exclude in this section. For example:

[tool.flit.sdist]
include = ["doc/"]
exclude = ["doc/*.html"]

These paths:

  • Always use / as a separator (POSIX style)

  • Must be relative paths from the directory containing pyproject.toml

  • Cannot go outside that directory (no ../ paths)

  • Cannot contain control characters or <>:"\\

  • Cannot use recursive glob patterns (**/)

  • Can refer to directories, in which case they include everything under the directory, including subdirectories

  • Should match the case of the files they refer to, as case-insensitive matching is platform dependent

Exclusions have priority over inclusions.

Note

If you are not using flit build but flit_core via another build frontend, Flit doesn’t doesn’t check the VCS for files to include but instead builds a ‘minimal’ sdist (which includes the files necessary to build a wheel). You’ll have to adapt your inclusion/exclusion rules to achieve the same result as you’d get with flit build.

External data section

New in version 3.7.

Data files which your code will use should go inside the Python package folder. Flit will package these with no special configuration.

However, sometimes it’s useful to package external files for system integration, such as man pages or files defining a Jupyter extension. To do this, arrange the files within a directory such as data, next to your pyproject.toml file, and add a section like this:

[tool.flit.external-data]
directory = "data"

Paths within this directory are typically installed to corresponding paths under a prefix (such as a virtualenv directory). E.g. you might save a man page for a script as (data)/share/man/man1/foo.1.

Whether these files are detected by the systems they’re meant to integrate with depends on how your package is installed and how those systems are configured. For instance, installing in a virtualenv usually doesn’t affect anything outside that environment. Don’t rely on these files being picked up unless you have close control of how the package will be installed.

If you install a package with flit install --symlink, a symlink is made for each file in the external data directory. Otherwise (including development installs with pip install -e), these files are copied to their destination, so changes here won’t take effect until you reinstall the package.

Note

For users coming from setuptools: external data corresponds to setuptools’ data_files parameter, although setuptools offers more flexibility.