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Standalone python

Use a Standalone Python Build

pipx can install applications under a Python interpreter downloaded from python-build-standalone instead of the system Python. Reach for this when the system Python is missing the version you asked for, or when the distro patched its Python in ways that break the application.

Choosing when to download

Set --fetch-python (or PIPX_FETCH_PYTHON) to one of three values:

Value Behaviour
never Default. Don't download. Use Python interpreters from PATH or the py launcher.
missing Look for the requested version locally first; download it when it isn't there.
always Skip the local search and use a standalone build for the requested version. 
# Download only when the requested version is missing locally
pipx install --python 3.13 --fetch-python=missing my-package

# Use a fresh standalone build, ignoring system Python
pipx install --python 3.13 --fetch-python=always my-package

# Set the policy for your shell session
export PIPX_FETCH_PYTHON=missing
pipx install --python 3.13 my-package

pipx unpacks the interpreter into its standalone cache. Manage cached interpreters with pipx interpreter list, pipx interpreter prune, and pipx interpreter upgrade (see the reference).

When --fetch-python=always is the right choice

  • CI runs where you don't want to depend on the runner's preinstalled Python.
  • Distros that strip optional modules (tkinter, lzma) from their packaged Python.
  • Air-gapped boxes where you have populated the standalone cache and want pipx to ignore the system Python.

Migrating from --fetch-missing-python

--fetch-missing-python and PIPX_FETCH_MISSING_PYTHON still work, but pipx warns and treats them as deprecated. They behave like --fetch-python=missing / PIPX_FETCH_PYTHON=missing. pipx errors out if you set both PIPX_FETCH_MISSING_PYTHON and PIPX_FETCH_PYTHON.