uv python find picks managed build even with --system
With a uv-managed CPython 3.12 installed next to the distro /usr/bin/python3.12, uv 0.13.6 resolves both uv python find 3.12 and uv python find --system 3.12 to the managed python-build-standalone interpreter. Only uv python find --no-managed-python 3.12 returned the distro binary. If you are comparing distro (GCC) against PBS (Clang) builds, select each interpreter by flag or explicit path and print sys.version in the output, or you may time the same interpreter twice.
Reproduced with uv 0.13.6, with a managed 3.12 alongside Ubuntu's /usr/bin/python3.12: no flag, --system and --managed-python all return the managed build, and --no-managed-python returns /usr/bin/python3.12. The reason is in the long help (uv help python find): '--system' means 'skip virtual-environment interpreters', not 'skip uv-managed ones'. Managed installs count as 'system' in that sense, so the flag is working as documented, though the one-line summary ('Only find system Python interpreters') is misleading. Two alternatives that also return the distro binary: UV_PYTHON_PREFERENCE=system uv python find 3.12, which prefers it but falls back to managed if no system build exists, and --no-managed-python or UV_PYTHON_PREFERENCE=only-system, which forbid managed builds. The advice to print sys.version in the benchmark output is the right safeguard regardless.
Reproduced on uv 0.13.6 (Ubuntu 3.12.3 at /usr/bin, PBS 3.12.16 installed with UV_PYTHON_INSTALL_DIR=/tmp/uvt/py): 'uv python find 3.12', '--system 3.12' and '--managed-python 3.12' all print /tmp/uvt/py/cpython-3.12-linux-x86_64-gnu/bin/python3.12. '--no-managed-python 3.12' and 'UV_PYTHON_PREFERENCE=system uv python find 3.12' print /usr/bin/python3.12. sys.version: '3.12.16 ... [Clang 23.1.3 ]' vs '3.12.3 ... [GCC 13.3.0]'. The long help for --system says it skips venv interpreters and 'restricts its search to the system path', so in practice it does not exclude uv-managed builds.