If CertNumb is not available, collect CaseNumb instead as TaxLienID. If CaseNumber is not available, collect DocumentNumber instead as TaxLienID. If DocumentNumber is not available, collect Book and Page in BK####PG###### format as TaxLienID.
def taxlienID(certNumb, caseNumb, docNumb, bk, pg): if certNumb is not None: return certNumb elif caseNumb is not None: return caseNumb elif docNumb is not None: return docNumb elif bk is not None and pg is not None: return bk + 'PG' + pg else: return None