Final Working Code

import rospy
import serial
from std_msgs.msg import Float64
from std_msgs.msg import String
import utm



def _parse_latitude(raw_latitude, direction):
    latitude = float(raw_latitude[0:2]) + float(raw_latitude[2:]) / 60.0
    if direction == 'S':
        latitude = -latitude
    return latitude

def _parse_longitude(raw_longitude, direction):
    longitude = float(raw_longitude[0:3]) + float(raw_longitude[3:]) / 60.0
    if direction == 'W':
        longitude = -longitude
    return longitude



if __name__ == '__main__':
    ### Start Rospy and get all the parameters.
    rospy.logdebug("Initializing Minicom")


    rospy.init_node('serial_connection', anonymous = True)
    serial_port = rospy.get_param('~port','/dev/ttyUSB0')
    serial_baud = rospy.get_param('~baudrate',4800)

    ### Read the serial ports with above parameters
    port = serial.Serial(serial_port, serial_baud, timeout=3)

    lat_pub = rospy.Publisher("Minicom"+'/lattitude', Float64, queue_size=5)
    lon_pub = rospy.Publisher("Minicom"+'/longitude', Float64, queue_size=5)
    alt_pub = rospy.Publisher("Minicom"+'/altitude', Float64, queue_size=5)
    utm_easting_pub = rospy.Publisher("Minicom"+'/utm_easting', Float64, queue_size=5)
    utm_northing_pub = rospy.Publisher("Minicom"+'/utm_northing', Float64, queue_size=5)
    zone_pub = rospy.Publisher("Minicom"+'/zone', Float64, queue_size=5)
    letter_pub = rospy.Publisher("Minicom"+'/letter', String, queue_size=5)


    # End the initialization Part
    rospy.logdebug("Initialization Complete")





    rospy.loginfo("Calculating lattitude, longitude and altitude")




    try:
        while not rospy.is_shutdown():
            data = str(port.readline())

            if data == '':
                rospy.logwarn("No data")
                print("data")
            else:

                if data.startswith('$GPGGA'):

                    datalist = data.split(',')

                    ### Saving Lattitude, longitude and Altitude in each reading in seperate lists.
                    lattitude = datalist[2]
                    latdirection = datalist[3]
                    finalLat = _parse_latitude(lattitude, latdirection)

                    longitude = datalist[4]
                    londirection = datalist[5]
                    finalLon = _parse_longitude(longitude, londirection)



                    altitude = float(datalist[9]) + float(datalist[11])

                    utm_values = utm.from_latlon(finalLat, finalLon)
                    utm_easting = utm_values[0]
                    utm_northing = utm_values[1]
                    utm_zone = utm_values[2]
                    utm_letter = utm_values[3]

                    print("Tejas")


                    lat_pub.publish(finalLat)
                    lon_pub.publish(finalLon)
                    alt_pub.publish(altitude)
                    utm_easting_pub.publish(utm_easting)
                    utm_northing_pub.publish(utm_northing)
                    zone_pub.publish(utm_zone)
                    letter_pub.publish(utm_letter)




    except rospy.ROSInterruptException:
        port.close()

    except serial.serialutil.SerialException:
        rospy.loginfo("Shutting down Minicom Node due to Serial Exception!!!")