python 时间转换

 def getDateTime(time_str):
     '''
     转换时间
     :param time_str:
     :return:
     '''
     if not isinstance(time_str,unicode):
         time_str = time_str.decode('utf-8')

     time_now = datetime.datetime.now()
     time_return = time_str

     if u'秒' in time_str:
         reg = r'(\d+)'
         t_second = re.search(reg, time_str)
         if t_second is not None:
             t_second = t_second.group(1)
             t_second = string.atoi(t_second)
             t_second = datetime.timedelta(seconds=t_second)
             time_return = time_now - t_second
             time_return = datetime.datetime.strftime(time_return, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'分钟' in time_str:
         reg = r'(\d+)'
         t_minute = re.search(reg, time_str)
         if t_minute is not None:
             t_minute = t_minute.group(1)
             t_minute = string.atoi(t_minute)
             t_minute = datetime.timedelta(minutes=t_minute)
             time_return = time_now - t_minute
             time_return = datetime.datetime.strftime(time_return, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'小时' in time_str:
         reg = r'(\d+)'
         t_hour = re.search(reg, time_str)
         if t_hour is not None:
             t_hour = t_hour.group(1)
             t_hour = string.atoi(t_hour)
             t_hour = datetime.timedelta(hours=t_hour)
             time_return = time_now - t_hour
             time_return = datetime.datetime.strftime(time_return, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'今天' in time_str:
         time_return = time_now.strftime('%Y-%m-%d %H:%M:%S')
         return time_return
     elif u'天前' in time_str:
         reg = r'(\d+)'
         t_day = re.search(reg, time_str)
         if t_day is not None:
             t_day = t_day.group(1)
             t_day = string.atoi(t_day)
             t_day = datetime.timedelta(days=t_day)
             time_return = time_now - t_day
             time_return = datetime.datetime.strftime(time_return, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'周' in time_str:
         reg = u'(\d+)'
         t_week = re.search(reg, time_str)
         if t_week is not None:
             t_week = t_week.group(1)
             t_week = string.atoi(t_week)
             t_week = datetime.timedelta(weeks=t_week)
             time_return = time_now - t_week
             time_return = datetime.datetime.strftime(time_return, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'月' in time_str:
         reg = r'(\d+)'
         t_num = re.search(reg, time_str)
         if t_num is not None:
             t_num = int(t_num.group(1))
             date_to = time_now.month - t_num
             # 判断是否跨年
             if date_to == 0:
                 month_to = 12
                 year_to = -1
             else:
                 month_to = date_to % 12
                 year_to = (date_to) / 12
             # 如果是最后一天31日，注意其他月份没有31日
             now_year = time_now.year+year_to
             d = calendar.monthrange(now_year,month_to)
             now_day = time_now.day
             if now_day > d[1]:
                 now_day = d[1]
             date_from = datetime.datetime(now_year,month_to,now_day,time_now.hour,time_now.minute,time_now.second)
             time_return = datetime.datetime.strftime(date_from, '%Y-%m-%d %H:%M:%S')
             return time_return
     elif u'年' in time_str:
         reg = u'(\d+)'
         t_year = re.search(reg, time_str)
         if t_year is not None:
             t_year = int(t_year.group(1))
             date_from = datetime.datetime(time_now.year-t_year,time_now.month,time_now.day,time_now.hour,time_now.minute,time_now.second)
             time_return = datetime.datetime.strftime(date_from, '%Y-%m-%d %H:%M:%S')
             return time_return
     else:
         # time_return = time_str
         int_year = time_now.year
         str_year = str(int_year)
         if time_str.find(str_year) < 0:
             time_return = str_year + '-' + time_str
         t_count = time_str.count(':')
         if t_count == 1:
             time_return += ':00'
         elif t_count == 0:
             time_return += ' 00:00:00'

         # 如果日期大于当前日期，则年份减1
         r_date = datetime.datetime.strptime(time_return, '%Y-%m-%d %H:%M:%S')
         if r_date > time_now:
             int_year_1 = int_year - 1
             time_return = time_return.replace(str_year, str(int_year_1))

         return time_return

 if __name__ == '__main__':
     print getDateTime('1周前')