Communication between arduino and pyserial. What's wrong?

Question

Python

Please help me figure out why the following python code only works if the delay (time.sleep(1)) is greater than 1 second?

import time
import serial

ser = serial.Serial(port='/dev/ttyUSB0',baudrate=115200)
ser.write(b'1')
while 1:
    ser.write(b'test\n')
    time.sleep(1)
    while ser.inWaiting() > 0:
        line = ser.readline()
        if line:
            print(line.decode().strip())

Sketch code for Arduino UNO:

void setup() {
  Serial.begin(115200);
}

void loop() {

String incomingData;

if (Serial.available() > 0) {  //если есть доступные данные

       incomingData = Serial.readString();
       Serial.println("123456789");
    }
}

Answer 1

After a lot of experimentation, we managed to achieve acceptable performance, 100 messages went for 0:00:00.601094:

#include <Arduino.h>

void setup() {
  Serial.begin(115200);
  Serial.println("Booting");
}

void loop() {


  while(Serial.available()){
    Serial.write(Serial.read());
  }
  delay(10);


}

python test code:

import time
import serial
import datetime

ser = serial.Serial(port='/dev/ttyUSB0', baudrate=115200)
received = []

ser.write(b'begin\n')
time.sleep(5)

start = datetime.datetime.now()
for i in range(1, 100):
    ser.write(b'test%i\r\n' % i)
    time.sleep(0.005)
    while ser.inWaiting() > 0:
        line = ser.readline()
        if line:
            received.append(line.decode().strip())

print(datetime.datetime.now() - start)
print(received)

ser.write(b'begin\n')
time.sleep(5)
This piece is needed so that the arduin (esp32 too) has time to reboot, because. dtr is related to software reset.
Read more here

Answer 2

This is normal for serial ports. While the data is being sent, while the arduina will send the answer.