From Wikitech

A Python package that contains custom modules to interact with the WMF production infrastructure.

It can be used in any script throughout the fleet as it doesn't require any special privilege to be run, as opposed to Spicerack and its Cookbooks and removes the need to re-implement each time the same functionalities over and over again.

For the current available modules see its documentation.

It's available both on PyPI as wmflib and as python3-wmflib and its source code lives on Gerrit in the operations/software/pywmflib repository.