Arduino Uno connected to PI 0 W - Sensor Data MQTT

[runboy]

Why would you need Putty? Don't they communicate fine without?

Arduino Sketch:

const int ledPin = 13
void setup()
{
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
}
void loop()
{
  Serial.println("Hello Pi");
  if (Serial.available())
  {
  flash(Serial.read() - '0');
  }
  delay(1000);
}
void flash(int n)
{
  for (int i = 0; i < n; i++)
  {
    digitalWrite(ledPin, HIGH);
    delay(100);
    digitalWrite(ledPin, LOW);
    delay(100)

Raspberry Code:

import serial
ser = serial.Serial('/dev/ttyACM0', 9600)
while True:
  print(ser.readline())

And to send from Raspberry to Arduino:

ser.write('5'.encode())

I would think that there must be tons of people out there who are pulling sensor data from an Arduino via a Pi, so I was just interested in their approach.