Ansible module to list groups in inventory (Python version :D)

#! /bin/python
#30 minutes Ansible module to list groups in inventory (Python version) :D
#You can print output like "pretty-print" outside Ansible by using:
#./listgroups | python -m json.tool 

import os
import re
import json

#get hosts inventory from ansible.cfg file.
def get_hosts_file(ansible_cfg):
  ansible_conf_file = open(ansible_cfg).readlines()
  regexp = re.compile('^hostfile')

  for line in ansible_conf_file:
    if regexp.search(line):
      return re.sub(r"(\n|(?<==)\s+)", "", line).split("=")[1]

hosts_file = get_hosts_file("ansible.cfg")
cat_hosts_file = open(hosts_file).readlines()

#Get groups from inventory file and add it to array. 
def groups_list():
  regexp = re.compile('^\[')
  gropus_array= []

  for line in cat_hosts_file:
    if regexp.search(line) is not None:
      matched_line = re.sub(r'[\n\[\]]', '', line)
      gropus_array.append(matched_line)
  return gropus_array

#Print output in json format.
print '{"Inventory Groups": ' + json.dumps(groups_list()) + '}'