Connecting Python to arduino - check if string is equal to do task

Question

I am passing a string from a computer with python(using pyserial) to my arduino uno and if it is equal to a set value, I need it to perform a task - I haven't even made it far enough to get the set values, I can't even get something to happen if it is passed at all. I just copied some of the blink code, to run if anything is received on serial and sometimes it works, and sometimes it doesn't, seemingly without reason. If anyone has an example of how to do this or knows where I am going wrong help would be appreciated.

Python Code

import serial
import time

def write():
    arduino = serial.Serial('/dev/ttyUSB0', 9600, timeout=.1)
    time.sleep(1) #give the connection a second to settle
    arduino.write(str.encode("Hello from Python!"))

write()

Arduino Uno Code

void setup() {
  Serial.begin(9600);
}
void loop() {
  if(Serial.available() > 0) {
    char data = Serial.read();
    char str[2];
    str[0] = data;
    str[1] = '\0';
    digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    delay(1000);                       // wait for a second
    digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
    delay(1000);     
  }
}

Answer 1

Add a delay(100) before your if(Serial.available() > 0) { statement.

More about this:

Your Arduino only has 1 core. If you do not have a delay() in your loop(), then the loop will take up 100% cpu usage all the time. This stops it from being able to execute background concurrent threads, e.g. to listen to Serial port, do bluetooth/wifi stuff, etc..

The delay() allows the main loop (or any thread) to sleep, so that the arduino's interrupt can execute other concurrent threads.