ModuleNotFoundError: No module named 'execnet'

TL;DR

Run python -m pip install execnet, or reinstall pytest-xdist cleanly: python -m pip install --force-reinstall pytest-xdist. execnet is xdist's worker-communication dependency; a partial or --no-deps install leaves it missing.

ModuleNotFoundError: No module named 'execnet'

Fix it

1. Install the missing dependency. Run python -m pip install execnet.

• Expected: Successfully installed execnet-....

1. Or reinstall the plugin with deps. Run python -m pip install --force-reinstall pytest-xdist.

• Expected: both pytest-xdist and execnet installed.

1. Verify. Run pytest -n 2 --collect-only -q.

• Expected: collection succeeds, workers spawn.

When this applies

• xdist is installed but workers fail immediately importing execnet.
• You installed with --no-deps or copied site-packages by hand.

When it does not apply

• If xdist itself is missing, install pytest-xdist first.

Tool compatibility

pytest-xdist 3.x requires execnet. Python 3.8+.

Why it happens

pip normally installs dependencies automatically, but --no-deps, --target hacks, or vendored environments can skip execnet while keeping xdist.

Edge cases

• Some minimal Docker images strip deps; add execnet explicitly to requirements.