def get_nps_from_papers(ids):
    npps = []
        
    for iid in ids:
        if not os.path.exists(os.path.join("NPs", iid+".xml")):
            extract_nps.extract_nps_single_paper(iid)
            
        with codecs.open(os.path.join("NPs", str(iid)+".xml"), mode='r', encoding='utf-8') as npfile:
            nps = dict([line.strip().split("\t") for line in npfile])

        npps.append(nps)
    return npps
 for iid in ids:
     year = f.get_year_for_id(iid)
     if year > YEAR:
         after.append(iid)
     else:
         before.append(iid)
         
 print len(before)
 print len(after)
 
 # Find all NPs in the after and before sets
 after_nps = set()
 for iid in after:
     print iid
     if not os.path.exists("NPs/"+iid+".xml"):
         extract_nps.extract_nps_single_paper(iid)
     
     npfile = open("NPs/"+iid+".xml", 'r')
     for line in npfile:
         np, count = line.strip().split("\t")
         after_nps.add(np)
          
          
 before_nps = set()
 for iid in before:
     print iid
     if not os.path.exists("NPs/"+iid+".xml"):
         extract_nps.extract_nps_single_paper(iid)
     
     npfile = open("NPs/"+iid+".xml", 'r')
     for line in npfile: