Publisher and Subscriber nodes don't seem to be communicating [closed]

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I made a publisher node that publishes Float64MultiArray message type to a topic zones. The script that contains this node constantly changes the .data portion of the message type. So for example, when it runs and I rostopic echo /zones, the .data portion of the message type looks like this [1.234,0.345](the floating point numbers constantly change). Int he terminal. So the publisher node obviously works. I'm testing to make a subscriber node to this topic zone.As seen here below

#!/usr/bin/python3
import rospy
from std_msgs.msg import Float64MultiArray
from rospy.numpy_msg import numpy_msg
import numpy as np

v=Float64MultiArray()

def callback(msg):
    global v
    v=msg


rospy.init_node("array_listener")


rospy.Subscriber("zones",Float64MultiArray, callback)

def hello():
    global v
    print(v.data[0])

hello()

when I run this script, v.data[0] is empty and gives and as a result the script gives back an index error on the terminal. v.data[0] is not supposed to be empty, it should have the first element in .data. I dont know why the subscriber does not seem to get information from the topic. I really need help on this.