How piplexed works

Below is a brief outline of the strategies employed to make piplexed work.

How does piplexed find pipx/uv local virtual environments ?

Piplexed uses the same paths and/or environment variables that pipx uses to determine the environment locations. For uv, the in-built uv tool dir is directly used.

How does piplexed find the version of each pipx installed package ?

When pipx installs a package it creates a pipx_metadata.json file in the venv, which contains among other things, the installed package name, version and the python version in the venv.

Piplexed finds and parses the pipx_metadata.json file.

How does piplexed find the version of each uv installed package ?

Unlike pipx, uv does not keep any kind of metadata or manifest file of versions, so piplexed has to use importlib.metadata which is unfortunately a little slower than parsing a metadata/manifest file.

How does piplexed determine what the latest PyPI version is ?

It turns out that determining the latest PyPI version of a package is a surprisingly hard thing to do consistently and reliably. There are 2 APIs for PyPI the json and simple API, with the simple API now being recommended for getting release information.

There is a python wrapper package for the simple api pypi-simple that returns a project pagre for each package containing it's version history. However there is no guarenteed order to the release versions.

Piplexed uses the simple API for PyPI (via the pypi-simple package), which provides an HTML (or JSON) page that lists all versions of package files (sdists and wheels) that have been uploaded. Because wheels are often platform specific, there is no guarantee that a suitable wheel distribution is available. Piplexed avoids the complications of obtating platform details and python versions and just looks at the sdist versions.

Piplexed employs the strategy recommended in PEP 700 to get the latest version, which utilises the packaging package to parse version numbers.

!!! note Most of this info was gleaned from looking at and researching Bernát Gábor's package pypi-changes, which also has heavily influenced this project.