You can add more condition to your search filter
Here is the sample but you can add more condition to fit your needs:
GroupSize= 5 basestring = "DerivedCategory eq 'BOND' and OriginalIssueCurrency eq 'USD' and ParentIndustrySector eq 'BANKS' and RIC ne null and ISIN ne null" srchfields = "RIC,ISIN,SeniorityType,NativeIdentifier,DerivedCategory,OriginalIssueCurrency,ParentIndustrySector" peergroupData = rdp.search(view=rdp.SearchViews.GovCorpInstruments, filter=basestring, top=GroupSize, select=srchfields) peergroupData
"RIC ne null" means "RIC field does not equal NULL value".