python对列表中的字典按[key]时间排序

#coding:utf-8
"""
    author：the5fire
    date:2012-10-10
    function:
        sort dict list by key
"""
import datetime

result_data = []
result_data.append({
    'id': 2,
    'create_time': '2012-10-8 11:09:22',
	})
result_data.append({
    'id': 3,
    'create_time': '2012-10-10 11:09:22',
    })
result_data.append({
    'id': 1,
    'create_time': '2012-10-1 11:09:22',
    })


def cmp_datetime(a, b):
    a_datetime = datetime.datetime.strptime(a, '%Y-%m-%d %H:%M:%S')
    b_datetime = datetime.datetime.strptime(b, '%Y-%m-%d %H:%M:%S')

    if a_datetime > b_datetime:
        return -1
    elif a_datetime < b_datetime:
        return 1
    else:
        return 0

import operator
print 'before',result_data
result_data.sort(cmp=cmp_datetime, key=operator.itemgetter('create_time'))
print 'after',result_data