title: masking alphanumeric strings to similar format
body: <p>i'm trying to impose a format on an alphanumeric string where digits become all 9's and the alphabets become A's.
  e.g. N43563 == A999
  e.g2. dhfgb85fb == AAAAA99AA
  something along these lines
  pytho based. i have tried regex but it was a bit confusing for me which is why i'm now asking for assistance</p>