Rate of function [Python]

edit

I need to change the frequency at which I enter to the function def detect_marker(self, msg)

Imagine that my code is like this (I deleted a lot of lines because this way would be easier to read):

#!/usr/bin/env python
from __future__ import division
import rospy
import sys
from std_msgs.msg import String
from std_msgs.msg import Empty
from geometry_msgs.msg import Twist
from ardrone_autonomy.msg import  Navdata


import threading
import tf
import time
from std_msgs.msg import Empty
from nav_msgs.msg import Odometry
from sensor_msgs.msg import Image, CameraInfo, CompressedImage
from cv_bridge import CvBridge, CvBridgeError
import cv2
from geometry_msgs.msg import Twist
from geometry_msgs.msg import PoseStamped
from geometry_msgs.msg import Pose

import numpy as np
import math

import time
from time import sleep


from ar_track_alvar_msgs.msg import AlvarMarkers




class gonnaGetDown():


    def __init__(self):


        self.velocity_publisher = rospy.Publisher('/cmd_vel', Twist, queue_size=10)
        self.orientation_publisher = rospy.Publisher('/cmd_vel', Twist, queue_size=10)

        print "b"

        global u_x_k, u_x_k_pre
        u_x_k, u_x_k_pre = 0, 0

        rospy.Subscriber('/ar_pose_marker', AlvarMarkers, self.detect_marker)

    def detect_marker(self, msg):
        print "c"

        u_x_k_pre = u_x_k
        u_x_k = u_x_k +1

        if not msg.markers:
            print "Tag not found"
            vel_msg = Twist()

            vel_msg.linear.x = 0.0
            vel_msg.linear.y = 0.0
            vel_msg.linear.z = 0.0
            vel_msg.angular.x = 0.0
            vel_msg.angular.y = 0.0
            vel_msg.angular.z = 0.0

            self.velocity_publisher.publish(vel_msg)
            return
        else:
            marker = msg.markers[0]
            print "d"


            self.velocity_publisher.publish(vel_msg)




if __name__ == '__main__':

    rospy.init_node('go_down', anonymous=True)



    try:
        rate = rospy.Rate(0.0001) 
        gonna_get_down = gonnaGetDown()
        while not rospy.is_shutdown():

            print "a"

            rate.sleep()


    except rospy.ROSInterruptException:
        rospy.loginfo("Node terminated.")

The most basic rqt graph is this https://imgur.com/LlWrhUW (ar_track_alvar node posts on /ar_pose_marker topic)

Leaving the code like that, it prints: a --> b --> c --> d --> c --> d --> c --> d --> c --> ... and so on

But the time between d's is 1 second. What if I want to make that much faster, like 10 times per second? Where do I change the frequency?

Thanks :D