taxid.py

import sys
from Bio import SeqIO
fh = open(sys.argv[1],"r") 
 
for gb_record in SeqIO.parse(fh, "genbank") :
  for (index, feature) in enumerate(gb_record.features) :
    if feature.type == 'source':
      print "\t".join([gb_record.name,feature.qualifiers['db_xref'][0].split(":")[1]])
      break