Lag in fetching serial data from Arduino I am working on a project based on Arduino and python3.6,two HC-SR04 sense the distance of palms and process the data using Arduino and send it through serial port to python3.6 ,python3.6 with the help of pyserial ,pyautogui based on data from arduino controls a game named supertuxcart,a racing game,basically the thought behind this is  controlling game with palms instead of keyboard or mouse .But the problem am facing is Arduino takes the distance measurement data from two HC-SR04(one for each hand) ultrasonic sensors, processes according and sends processed data through serial port to python3.6 ,there while running the my python script i open the game to check if its working ,it works, but there is lag in data received from arduino thus turn the game messy.

here is arduino code am using with NewPing library 

#include &lt;NewPing.h&gt;
int trig1=9;
int echo1=6;
int trig2=7;
int echo2=5;
int R;
int L;
NewPing right(9,6,100);
NewPing left(7,5,100);
void setup() {

  pinMode(9,OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(6,INPUT);
  pinMode(5,INPUT);

}

void loop() {
  Serial.begin(9600);
  //Serial.println("hi,am arduino");
  R=right.ping_cm();
  L=left.ping_cm();
  //Serial.println(R);
  //Serial.println(L);
  delay(0000);
 if (R==0 &amp;&amp; L==0){
    Serial.println('0');
  }
  else if(R&lt;L&amp;&amp;L-R&gt;5){
    Serial.println('1');
  }
  else if(R&gt;L&amp;&amp;R-L&gt;5){
    Serial.println('2');

delay(3000);

  }

}


Here is python3.6 code am using 

import serial
import pyautogui
import time

Arduino = serial.Serial('/dev/ttyACM0', 9600)
time.sleep(0)
print(Arduino.readline())
pyautogui.keyDown('up')
while 1:
    Data = Arduino.readline()
    print(Arduino.readline())

    if Data == b'0\r\n':
        pyautogui.keyUp('up')
        pyautogui.keyUp('right')
        pyautogui.keyUp('left')
        break
    elif Data == b'1\r\n':
        pyautogui.keyUp('left')
        pyautogui.keyDown('right')
    elif Data == b'2\r\n':
        pyautogui.keyUp('right')
        pyautogui.keyDown('left')
A couple of things jump out at me:


You only need to run Serial.begin(9600) once in setup() - never in loop() like that.
Your delay(3000) will be causing a 3 second delay when R&gt;L&amp;&amp;R-L&gt;5. 
You don't need to constantly send the data over and over again. You just need to send it once and once only when the state changes.


At the moment you're sending something like:

0000000000000000000000000000000000000000001111111111111111111111111111111111111111111111111111111111111111111111111111111111111100000000000000000000000000000000000000000000000000000000000000000002222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222200000000000000000000000000000000000000000000000000000000000000


when all you really need to do is send 01020. Remember what the state is and only send anything when that state changes from one iteration to the next. And never ever use delay().