I gather that one of the values of COBOL is that the typical program runs on mini/mainframe computers with the guarantee from IBM or whoever that the code writt

I gather that one of the values of COBOL is that the typical program runs on mini/mainframe computers with the guarantee from IBM or whoever that the code written in 1970 will still perform on a 2020 computer the exact same way - inputs, outputs, etc. Python does not have the same commitment or track record.