NameError: global name 'NAME' is not defined

edit

hello, I'm trying to publish data of my GPS but it appears this error

NameError: global name 'hora' is not defined

Anybody help me please :)

My code is this:

#!/usr/bin/env python
import rospy
import serial
import pynmea2
import roslib; roslib.load_manifest('ceres_pkg')
from std_msgs.msg import String
from geometry_msgs.msg import Point

serialStream = serial.Serial("/dev/ttyAMA0",9600,timeout=0.5)

 class GPS(object):
    def __init__(self):
        self.pub_ = rospy.Publisher("/dat_gps", Point, queue_size = 1)
        return
    def start(self):
        sentence = serialStream.readline()
        global hora,lat,lon
        if sentence.find('GGA') > 0:
            data = pynmea2.parse(sentence)
            hora = data.timestamp
            lat = data.latitude
            lon = data.longitude
        pos_msg = Point(hora, lat, lon)
        loop_rate = rospy.Rate(1)
        while not rospy.is_shutdown():
            self.pub_.publish(pos_msg);
            loop_rate.sleep()
        return

if __name__ == '__main__':
    rospy.init_node('GPS_py', log_level=rospy.INFO)
    rospy.loginfo("%s: starting GPS node", rospy.get_name())
    Gps = GPS()
    Gps.start()