The value of exposing a calculation like this is not that it is hard to compute — it is that the model will otherwise attempt the algebra itself and be confidently wrong about a rearrangement. Handing it the closed form, with the inverse solutions alongside, removes that failure. Narrow, checkable, and it costs almost nothing to leave connected.
A Python package for a specific calculation in fluid mechanics: the permeability of a porous medium, derived from Darcy's law using the seepage distance method.
The permeability calculation and its inverses — solving for the time a front takes, or for how far it has travelled at a given moment.
Python, installed from PyPI. GPL-3.0 licensed. Documentation is available in both English and Chinese.
One command — pip install permeability