how to remove the delay in obtaining data from the Arduino via COM?

I have an Arduino connected to the joystick. Arduino sends the data via COM port to my PC. On PC, the data processed by the program in Python, in which the circle moving with joystick. The fact is that after a few minutes there is a delay between the joystick and circle. Code for Arduino #define axis_X 0 #define axis_Y 1 int value_X, value_Y = 0; void setup() { Serial.begin(9600); } void loop() { value_X = analogRead(axis_X); Serial.print(value_X, DEC); Serial.print("|"); value_Y = analogRead(axis_Y); Serial.print(value_Y, DEC); Serial.print("n"); delay(20); } Code for PC import Tkinter as tk import serial import os import sys import time #connect to COM ser = serial.Serial('COM11', 9600, dsrdtr = 1,timeout = 0) def data(): time.sleep(0.02) serialline = ser.readline().split("n") coord = [] if serialline[0]: string = serialline[0] coord = string.split("|") return coord #create window root = tk.Tk() canvas = tk.Canvas(root, width=1000, height=700, borderwidth=0, highlightthickness=0, bg="black") canvas.grid() def _create_circle(self, x, y, r, **kwargs): return self.create_oval(x-r, y-r, x+r, y+r, **kwargs) tk.Canvas.create_circle = _create_circle r = 50 x = 100 y = 100 sm = 200 cir = canvas.create_circle(x, y, r, fill="blue", outline="#DDD", width=1) root.wm_title("Circles and Arcs") while 1: coord = data() x = int(coord[0])/5 y = int(coord[1])/5 canvas.coords(cir,x+ sm,y+sm,x+sm + 2*r,y+sm + 2*r) root.update() How to solve this problem?