Implementation of APC is now available in PySCF. Candidate HF orbitals are then ranked in importance by their orbital entropies, with this ranking used to choose an active space meeting some user-defined size requirement (e.g., (12,12)). Here, to select consistent active space sizes between geometries we employ a simple size requirement in which for an (A,B) active space, the A/2 highest-entropy doubly occupied orbitals and the B -A/2 highest-entropy virtual orbitals are added to the active space; we refer to these active spaces as APC-(A,B). CASSCF calculations initialized from these active spaces in the cc-pVDZ basis were then carried out in PySCF. These CASSCF wave functions were then used for the calculation of MC-PDFT (tPBE) and NEVPT2 energies, also implemented in PySCF and PySCF-Forge. Multiconfigurational (or equivalently, multireference (MR)) character in the resulting wave functions is calculated via the M -diagnostic, which measures multiconfigurational character as a function of the natural orbital occupancies: