import sys
import argparse

def Parser():
  the_parser = argparse.ArgumentParser(description="add label to last column of file")
  the_parser.add_argument('--input', required=True, action="store", type=str, help="input tabular file")
  the_parser.add_argument('--output', required=True,  action="store", type=str, help="output file path")
  the_parser.add_argument('--label', required=True, action="store", type=str, help="label to add in last column")
  the_parser.add_argument('--header', action="store", type=str, help="column label for last column")
  args = the_parser.parse_args()
  return args

args=Parser()

input=open(args.input)
output=open(args.output, 'w')
for i,line in enumerate(input):
  line=line.strip('\n')
  if (i==0) and (args.header!=None):
    line=line+'\t'+args.header
  else:
    line=line+'\t'+args.label
  print >>output, line
input.close()
output.close()