ImportError: cannot import name 'POLARS_STORAGE_CONFIG_KEYS' from 'polars.io.cloud._utils'

TL;DR: your polars install is a mix of versions from a partial upgrade. Uninstall polars fully, delete leftovers, and install one clean version.

The error

ImportError: cannot import name 'POLARS_STORAGE_CONFIG_KEYS' from 'polars.io.cloud._utils'

Fix it

1. Uninstall polars:

   pip uninstall -y polars

Expected: reports removal.

1. Check site-packages for a leftover polars folder and delete it by hand.
2. Install fresh:

   pip install polars

Expected: install completes.

1. Verify:

   python -c "import polars; print(polars.__version__)"

Expected: prints the version, no error.

When this applies

Use this when import polars itself raises the POLARSSTORAGECONFIG_KEYS error, which signals mixed install files.

When it does not apply

If your own code imports from polars.io.cloud._utils, stop; it is a private module. If the error is a different missing name, check the polars version first.

Compatibility

Any polars version; this is an install-hygiene issue.

Root cause

polars.io.cloud._utils is a private module whose contents change between releases. A partial upgrade (or pip plus conda both installing polars) leaves old and new files side by side, and the mismatched modules cannot import each other's names.

Edge cases

polars ships a compiled binary per version; mixing the python files of one version with the binary of another produces exactly this class of error. In docker, pin the polars version so rebuilds stay consistent.