How to publish array of velocities?

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Hello guys, so I am very new to ROS and python. Now I understand the following: to publish on a topic, for example Twist() you write something like this and you publish one value for a couple of seconds (4 seconds in this case):

   1 #!/usr/bin/env python
   2 import rospy
   3 from geometry_msgs.msg import Twist
   4 
   5 def move():
   6     # Starts a new node
   7     rospy.init_node('robot_cleaner', anonymous=True)
   8     velocity_publisher = rospy.Publisher('/turtle1/cmd_vel', Twist, queue_size=10)
   9     vel_msg = Twist()
  10
  11     vel_msg.linear.x = 0.5
  12     vel_msg.linear.y = 0
  13     vel_msg.linear.z = 0
  14     vel_msg.angular.x = 0
  15     vel_msg.angular.y = 0
  16     vel_msg.angular.z = 0
  17     
  18     now = rospy.Time.now()
  19
  20     while rospy.Time.now() < now + rospy.Duration.from_sec(4):
  21     pub.publish(vel_msg)
  22     
  23 move()

But so instead of publishing one velocity for a couple of seconds I want now to publish like an array of velocities. For example vel_msg.linear.x = [0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9]. So every timestep there will be another velocity published until the last value is reached.

How can you do this? And maybe another question: how do you know the timestep that ROS is using between the values of the array? Thanks in advance!