python list使用樣本 list中找連續的數字

線上有個需求，格式化,從一堆s1,s100-s199中找出連續的服並且格式化顯示出來，如：

神魔：S106-109,s123,s125
禦劍: s106-109,s123,s125

代碼如下:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# 2014/01/15 14:15
import sys
from itertools import *
from operator import itemgetter
def parse(filename):
d = {}
for line in open(filename, 'r'):
_line = line.split()
d.setdefault(_line[0], []).append(_line[1])
for key in d.keys():
data = sorted(map(lambda x: int(x[1:]), d[key]))
sys.stdout.write(key + " ")
for k, g in groupby(enumerate(data), lambda (i, x): i - x):
ret = map(itemgetter(1), g)
if len(ret) > 1:
sys.stdout.write("S%d-%d," % (ret[0], ret[-1]))
elif len(ret) == 1:
sys.stdout.write(str("S%s") % ret[0] + ",")
sys.stdout.write('\n')
if __name__ == "__main__":
filename = sys.argv[1]
parse(filename)

