`uv --python` and `uv python pin` fail if Python3.6 is found on the system

[jramcast]

Summary

I have Python 3.10 installed at /usr/local/bin/python
Python3.6 is also available at /usr/bin/python3

Expected behavior: uv ignores the 3.6 installation.

Actuall behavior. When I try to run a command by using a specific python version, the command fails

uv -v run --python 3.9 python --version
DEBUG uv 0.5.23
DEBUG No project found; searching for Python interpreter
DEBUG Searching for Python 3.9 in virtual environments, managed installations, or search path
DEBUG Searching for managed installations at `.local/share/uv/python`
DEBUG Found `cpython-3.10.4-linux-x86_64-gnu` at `/usr/local/bin/python3` (search path)
DEBUG Skipping interpreter at `/usr/local/bin/python3` from search path: does not satisfy request `3.9`
DEBUG Found `cpython-3.10.4-linux-x86_64-gnu` at `/usr/local/bin/python` (search path)
DEBUG Skipping interpreter at `/usr/local/bin/python` from search path: does not satisfy request `3.9`
DEBUG Failed to inspect Python interpreter from search path at `/usr/bin/python3` 
DEBUG Skipping bad interpreter at /usr/bin/python3 from search path: Python 3.6.8 is not supported. Please use Python 3.8 or newer.
DEBUG Failed to inspect Python interpreter from search path at `/bin/python3` 
DEBUG Skipping bad interpreter at /bin/python3 from search path: Python 3.6.8 is not supported. Please use Python 3.8 or newer.
error: Failed to inspect Python interpreter from search path at `/usr/bin/python3`
  Caused by: Can't use Python at `/usr/bin/python3`
  Caused by: Python 3.6.8 is not supported. Please use Python 3.8 or newer.

Platform

Linux 6.12.5-200.fc41.x86_64 x86_64 GNU/Linux

Version

uv 0.5.23

Python version

Python 3.10.4

[zanieb]

Thanks for the report! This is surprising.

Do you have a Python 3.9 interpreter available?

Does this reproduce on uv 0.5.21? I am suspicious of #10716

[jramcast]

No, Python 3.9 is not initially available in the system.

Downgrading to 0.5.21 solves the issue:

$ uv run --python 3.9 python --version
Python 3.9.21

More verbose output:

$ uv -v run --python 3.9 python --version
DEBUG uv 0.5.21
DEBUG No project found; searching for Python interpreter
DEBUG Searching for Python 3.9 in virtual environments, managed installations, or search path
DEBUG Searching for managed installations at `/home/user/.local/share/uv/python`
DEBUG Found `cpython-3.10.4-linux-x86_64-gnu` at `/usr/local/bin/python3` (search path)
DEBUG Skipping interpreter at `/usr/local/bin/python3` from search path: does not satisfy request `3.9`
DEBUG Found `cpython-3.10.4-linux-x86_64-gnu` at `/usr/local/bin/python` (search path)
DEBUG Skipping interpreter at `/usr/local/bin/python` from search path: does not satisfy request `3.9`
DEBUG Failed to inspect Python interpreter from search path at `/usr/bin/python3` 
DEBUG Skipping bad interpreter at /usr/bin/python3 from search path: Can't use Python at `/usr/bin/python3`
DEBUG Failed to inspect Python interpreter from search path at `/usr/bin/python` 
DEBUG Skipping bad interpreter at /usr/bin/python from search path: Can't use Python at `/usr/bin/python`
DEBUG Failed to inspect Python interpreter from search path at `/bin/python3` 
DEBUG Skipping bad interpreter at /bin/python3 from search path: Can't use Python at `/bin/python3`
DEBUG Failed to inspect Python interpreter from search path at `/bin/python` 
DEBUG Skipping bad interpreter at /bin/python from search path: Can't use Python at `/bin/python`
DEBUG Requested Python not found, checking for available download...
DEBUG Acquired lock for `/home/user/.local/share/uv/python`
DEBUG Using request timeout of 30s
INFO Fetching requested Python...
DEBUG Downloading https://github.com/astral-sh/python-build-standalone/releases/download/20250115/cpython-3.9.21%2B20250115-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz to temporary location: /home/user/.local/share/uv/python/.temp/.tmppU5lnb
DEBUG Extracting cpython-3.9.21%2B20250115-x86_64-unknown-linux-gnu-install_only_stripped.tar.gz
DEBUG Moving /home/user/.local/share/uv/python/.temp/.tmppU5lnb/python to /home/user/.local/share/uv/python/cpython-3.9.21-linux-x86_64-gnu
DEBUG Released lock at `/home/user/.local/share/uv/python/.lock`
DEBUG Using Python 3.9.21 interpreter at: /home/user/.local/share/uv/python/cpython-3.9.21-linux-x86_64-gnu/bin/python3.9
DEBUG Running `python --version`
Python 3.9.21
DEBUG Command exited with code: 0

[zanieb]

Great thanks!

[mpetruc]

Similar issue with the uv 0.6.1:

uv -v pip install -r requirements.txt
DEBUG uv 0.6.1
DEBUG Searching for default Python interpreter in virtual environments
DEBUG Failed to inspect Python interpreter from first executable in the search path at `/usr/bin/python3`
DEBUG Skipping bad interpreter at /usr/bin/python3 from first executable in the search path: Python 3.6.8 is not supported. Please use Python 3.8 or newer.
DEBUG Ignoring Python interpreter at `/usr/bin/python3.11`: system interpreter not explicitly requested
error: Failed to inspect Python interpreter from first executable in the search path at `/usr/bin/python3`
  Caused by: Can't use Python at `/usr/bin/python3`
  Caused by: Python 3.6.8 is not supported. Please use Python 3.8 or newer.

[zanieb]

@mpetruc Sorry about that. Can you please open a new issue with more details per #9452?