Pytry

#!/opt/local/bin/python
# -*- coding: utf-8 -*-

import os
import math
import csv
import sys

# Lire le fichier de ranges...
with open(sys.argv[1], "rb") as infile, open("IRanges.txt", "wb") as outfile:
    reader = csv.reader(infile)
    writer = csv.writer(outfile, quoting=False)
    
    writer.writerow(["Start\tEnd\tLength"])
    #Initialize variables
    IRval_s=0
    IRval_e=0
    idx=0
    lgth=0
    
    for i, line in enumerate(reader):
        print "Processing line " + str(i) + " : " + ''.join(line) + "\n"
        # skip first line corresponding to comments 
        if i < 1: continue
        #if i > 20: break
        IRrange = line[0].split()
        # traitement des lignes paires (le +1 est parce qu'on a skippé la premiere ligne)
        if (i+1) % 2 == 0:
            IRval_s=int(IRrange[1])+1
        else:
            IRval_e=int(IRrange[0])-1
            lgth=IRval_e - IRval_s + 1
            
            newline=str(IRval_s) + "\t" + str(IRval_e) + "\t" + str(lgth)
            print "Ici c'est: " + newline
            writer.writerow([newline])
            #Reset variables
            IRval_s=0
            IRval_e=0
            lgth=0

infile.close()
outfile.close()