Flit

Spec sheet

Purpose

Flit is a simple way to put Python packages and modules on PyPI, aiming to reduce packaging effort and common mistakes.Read 9 Oct 2026 · flit.pypa.io

Integrations

Flit uses pip for installation and supports uploading to PyPI, TestPyPI, or another configured package index.Read 9 Oct 2026 · flit.pypa.io

Automated publishing

Flit supports configuring upload servers and credentials through environment variables for automated releases, while warning that environment variables can expose passwords to other scripts and libraries in the environment.Read 9 Oct 2026 · flit.pypa.io

Build

The `flit build` command builds wheel and source distribution files.Read 8 Oct 2026 · flit.pypa.io

Builds

The `flit build` command builds a wheel and source distribution, with an option to build either format alone.Read 9 Oct 2026 · flit.pypa.io

Credential handling

Flit tries to store upload passwords securely using the keyring library; without keyring, it prompts for a password for each upload.Read 9 Oct 2026 · flit.pypa.io

Intended use

Flit focuses on pure Python packages with no build steps, such as compiling C code or bundling JavaScript.Read 9 Oct 2026 · flit.pypa.io

Limit: build steps

Flit cannot be used for packages that require a build step.Read 8 Oct 2026 · flit.pypa.io

Limit: dependencies

Flit does not manage dependencies, which must be added to `pyproject.toml` by hand.Read 8 Oct 2026 · flit.pypa.io

Notable limitation

Flit cannot be used for packages that need a build step and does not manage dependencies automatically; dependencies must be added to `pyproject.toml` by hand.Read 9 Oct 2026 · flit.pypa.io

Package contents

Flit automatically includes subpackages and data files within a package.Read 8 Oct 2026 · flit.pypa.io

Packaging

Flit packages one importable module or package at a time and automatically includes its subpackages and package data files.Read 9 Oct 2026 · flit.pypa.io

Publishing

The `flit publish` command builds and uploads packages to PyPI or another configured package repository.Read 9 Oct 2026 · flit.pypa.io

Python requirement

The Flit command line tool requires Python 3.Read 9 Oct 2026 · flit.pypa.io

Reproducible builds

Flit says wheels built from the same source code can be byte-for-byte identical, with file timestamps noted as a caveat that can be overridden using `SOURCE_DATE_EPOCH`.Read 9 Oct 2026 · flit.pypa.io

Setup

The `flit init` command helps set up package information in a `pyproject.toml` file.Read 9 Oct 2026 · flit.pypa.io

Target packages

Flit focuses on pure Python packages that have no build steps.Read 8 Oct 2026 · flit.pypa.io

Version metadata

Flit can obtain a package’s version from its `__version__` attribute.Read 9 Oct 2026 · flit.pypa.io

Windows support

The `--pth-file` install option works on Windows, where symlinks typically are not allowed.Read 8 Oct 2026 · flit.pypa.io

Where Specifiction places it

• Python Package Managers#24 of 277.2