ToolPythonIntermediate Surface temperature of an airless planet: day, night, and below the ground print("layers changing:", np.count_nonzero(rhs(0.0, T_flat)), "of", z.size)
ToolPythonIntermediate findiff.PDE with mixed boundary conditions: seepage under a dam fixed = np.count_nonzero(bc.lhs[n].toarray(), axis=1) == 1 # a Dirichlet row holds a single 1