PDM author here, if anyone want to know the advantage of __pypackages__ over virtualenv-based tools(venv, virtualenv, poetry, pipenv), here it is: The fact that virtualenvs come with a cloned(or symlinked) interpreter makes it vulnerable when users want to upgrade the host interpreter in-place unless you keep all the old installations in your system, which is what pyenv is doing. You can imagine how many interpreters, including virtualenv-embedded ones are on your machine.

You can regard __pypackages__ as a virtualenv WITHOUT the interpreter, it can easily work with any python interpreter you choose as long as it has the same major.minor version as the packages folder.