Formulas is a package that serves as both a collection of common formulas in physics and astrophysics and the machinery to create new formulas from scratch or from combinations of them.
Formula objects are combinations of a SymPy-based mathematical formula with variables and parameters, along with the ability to set the parameters to particular values. The parameters may be set to float values or to unitful quantities, the latter provided by the yt and/or AstroPy packages.