Reading data from a service via python

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I need help understanding how to call and read from a service.

I created a package which launches the map_server node with a map I created from the gmapping node. I need to read data from the /static_map service (of type nav_msgs/GetMap) which is provided by map_server, using the following code:

#!/usr/bin/env python
import rospy

from nav_msgs.srv import GetMap

def printData(datas):
    rospy.loginfo("printing : .... ")
    return

def testing():
    rospy.init_node('map_lists')

    rospy.wait_for_service('static_map')
    try:
        rospy.ServiceProxy('GetMap', 'static_map')
    except rospy.ServiceException as e:
        rospy.logerr("Service call failed: %s"%e)

    print "testing ... testing"
    rospy.spin()

if __name__ == '__main__':
    testing()

My problem is my printData callback is not being called because my ServiceProxy function call is wrong. The ServiceProxy api says ServiceProxy(name, service_class, persistent=False, headers=None)and I referred to https://answers.ros.org/question/2630... but neigther helped to clarify how to correctly call ServiceProxy.

I need help, please.