Flit is itself packaged using Flit, as are some foundational packaging tools such as pep517. So where can you start if you need to install everything from source?


For most users, pip handles all this automatically. You should only need to deal with this if you’re building things entirely from scratch, such as putting Python packages into another package format.

The key piece is flit_core. This is a package which can build itself using nothing except Python and the standard library. From an unpacked source archive, you can make a wheel by running:

python -m flit_core.wheel

And then you can install this wheel with the script included in the sdist (or by unzipping it to the correct directory):

# Install to site-packages for this Python:
python dist/flit_core-*.whl

# Install somewhere else:
python --installdir /path/to/site-packages dist/flit_core-*.whl

As of version 3.6, flit_core bundles the tomli TOML parser, to avoid a dependency cycle. If you need to unbundle it, you will need to special-case installing flit_core and/or tomli to get around that cycle.

After flit_core, I recommend that you get installer set up. You can use python -m flit_core.wheel again to make a wheel, and then use installer itself (from the source directory) to install it.

After that, you probably want to get build and its dependencies installed as the goal of the bootstrapping phase. You can then use build to create wheels of any other Python packages, and installer to install them.