How to communicate between a python script and arduino

| Component        | Description                                               |
| ---------------- | --------------------------------------------------------- |
| Arduino Board    | Any (Uno, Nano, Mega, etc.)                               |
| Connection       | USB cable                                                 |
| Python Package   | `pyserial` → Install via: `pip install pyserial`          |
| Baud Rate        | 9600 (must be the same on both sides)                     |
| Port (Windows)   | `COM3`, `COM4`, etc. (Check Device Manager)               |
| Port (Linux/Mac) | `/dev/ttyUSB0`, `/dev/ttyACM0`, etc. (Check via terminal) |
 

Ardiono Code:- 

void setup() {
  Serial.begin(9600);  // Start Serial Communication
}

void loop() {
  if (Serial.available()) {
    String data = Serial.readStringUntil('\n');  // Read incoming data from Python
    Serial.print("Received: ");
    Serial.println(data);  // Echo back to Python
  }
  delay(100);  // Optional: avoid buffer overload
}
 

Python Code:-

import serial
import time

# Create Serial connection (update 'COM3' if needed)
arduino = serial.Serial(port='COM3', baudrate=9600, timeout=1)
time.sleep(2)  # Wait for Arduino to initialize

def send_to_arduino(data):
    arduino.write((data + '\n').encode())  # Send string with newline
    time.sleep(0.1)
    if arduino.in_waiting:
        response = arduino.readline().decode().strip()
        print("From Arduino:", response)

# Example usage
send_to_arduino("Hello Arduino")
send_to_arduino("123")

 

| Python Sends    | Arduino Responds          |
| --------------- | ------------------------- |
| `Hello Arduino` | `Received: Hello Arduino` |
| `123`           | `Received: 123`           |