Pretty cool but I think SymPy is more practical w.r.t. to formula transformations and rendering is as good in Jupyter notebooks. If it only had as good pattern matching and substitution rules as Mathematica...
Sympy is for solving an original solution. handcalcs is for plugging numbers into formulas. Next major milestone is integrating sympy with handcalcs so it is easy to transition from the sympy steps to the calculation steps.