ModuleNotFoundError: No module named 'polars'

Not specified by the original author.

TL;DR: polars is not installed in the environment running your code. Run pip install polars (in the right environment) and the import works.

The error

ModuleNotFoundError: No module named 'polars'

Fix it

1. Confirm which python runs your code:

   which python && python --version

   Expected: shows the interpreter you mean to use.

2. Install polars into it:

   python -m pip install polars

   Expected: install completes.

3. Verify:

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

   Expected: prints the version.

4. In CI, add polars to the requirements file so the next run does not regress.

When this applies

Use this when import polars raises the missing-module error, especially in CI or fresh containers.

When it does not apply

If polars is installed but the import still fails, you are in the wrong environment; check which pip and which python. If the error is a different message, that is a separate issue.

Compatibility

All polars versions; wheels exist for major platforms and Python versions.

Root cause

The code runs under an interpreter whose site-packages lack polars. CI images, new virtualenvs, and notebooks attached to the wrong kernel are the usual suspects.

Edge cases

Using python -m pip instead of bare pip guarantees the package lands in the interpreter you checked. On very old CPUs, plain polars may then hit the illegal-instruction issue; polars-lts-cpu covers that case.

A commit in chmoses98/nfl-edge-finder's CI history hit ModuleNotFoundError: No module named 'polars' when the pipeline ran in an environment where polars had not been installed. The verified fix: installing polars into the environment the code actually runs in (pip install polars, and adding it to the CI requirements so it persists) resolved the import. Source: https://github.com/chmoses98/nfl-edge-finder