Fabric hosts file parsing

fabfile.py

import re

hosts_list = []
with open('hosts_file') as f:
  for line in f:
    if not (line.strip()=='' or line.startswith('#')):
      if "[" in line:
        prefix = line.split('[')[0]
        m = re.search(r"\[([0-9\-]+)\]", line)
        a = m.group(1)
        start, end = a.split('-')
        start_i = int(start)
        end_i = int(end) + 1
        if start.startswith('0'):
          for i in range(start_i, end_i):
            val = prefix + "%02d" % i
            hosts_list.append(val)
        else:
          for i in range(start_i, end_i):
            val = prefix + "%d" % i
            hosts_list.append(val)
      else:
        hosts_list.append(line)
env.hosts = hosts_list

Allow blank space in hosts_file