title: Iterating to a numpy list
body: <p>I've been looking around but I have still faced problems with understanding the error in my code. I am trying to get get_pos values listed in pos_list array of size (numstep, N, 3). The values for get_pos is clearly checking as numstep,N,3 but when I call for pos_list at the bottom, it only prints out the last value. Is there anything I've missed?</p>
  <pre><code> def get_pos(p_list, N):
      sys_position = np.zeros([N,3])
      for i in range(N):
          sys_position[i] = p_list[i].pos
          
      return sys_position
  
   pos_list = np.zeros([numstep, N, 3])
  
   for num in range(numstep):
       # Update particle position
       update_pos(p_list, dt, N)
          
       # Update force
       force_new = get_force(p_list, dt, N)
  
       # Update particle velocity by averaging
       # current and new forces
       update_vel(p_list, 0.5*(force+force_new), dt, N)
          
      # Re-define force value
          force = force_new
          # Increase time
          time += dt
                                                                       
          print(get_pos(p_list,N))
  
          # Append information to data lists
          pos_list = get_pos(p_list, N)
       
          
      print(pos_list)
  
  
  </code></pre>
  <p>ANy help would be appreciated I've been staring at this for far too long.</p>
  <p>EDIT: attaching get_pos; function to list down array of position. Calling get_pos gets me the array of position at time t in the range of (0, numstep).</p>