README.md

We suggest installing the pyenv-suffix plugin to distinguish between free-threaded and "standard" builds of CPython 3.13:

CONFIGURE_OPTS="--disable-gil" PYENV_VERSION_SUFFIX='-nogil' \
pyenv install -v --debug 3.13-dev

You can then "activate" the installed free-threaded python in your global shell environment with

pyenv global 3.13-dev-nogil-debug

Or locally in a single directory with a .python-version file or with

pyenv local 3.13-dev-nogil-debug

Note that debug builds of python are substantially slower. You can drop --debug from the pyenv install invocation if you would like an optimized build. The resulting pyenv environments will not have a -debug suffix in their names.

You can simultaneously install the build of python with the GIL enabled with

pyenv install -v --debug 3.13-dev

The resulting environment can be activated with

pyenv global 3.13-dev

If you need to install a CPython development tree, either locally or on GitHub, you can do so using a custom definition, e.g. based on the definition for 3.13-dev. Replace the repository used in that definition with a CPython fork or local clone and replace 3.13 with the branch you would like to build. The commit you would like to build must have a branch pointing to it. If your custom definition should have the same name as the original definition, but with edited paths and branch names. Install it with e.g. this command:

CONFIGURE_OPTS=--disable-gil PYENV_VERSION_SUFFIX='-nogil-branch' pyenv install -v ./3.13-dev

And it will be available to activate via the pyenv CLI with the name 3.13-dev-nogil-branch.