asdf vs eselect-python

asdf is a free, open-source version manager for Linux and macOS. It gives project teams one command interface and a shared `.tool-versions` file for selecting exact versions of multiple tools and runtimes. Plugins support tools such as Node.js, Ruby, and Elixir, while the plugin API allows additional tools. When a command runs, asdf searches for configuration from the current directory upward toward the home directory, then uses shims to launch the selected executable. Existing `.ruby-version`, `.nvmrc`, and `.node-version` files can be supported per plugin. Listed shell support includes Bash, ZSH, Fish, and Elvish, with completions. A GitHub Action uses `.tool-versions` in CI/CD workflows. Installation options include Homebrew, Zypper, Pacman, precompiled binaries, Go, and source builds. asdf manages tool versions rather than system packages or upstream dependencies. If no version is set, execution errors unless the tool is configured as `system`.

eselect-python has no write-up on Specifiction yet; its figures are above.