Code with wiring diagrams

const int LED = 13;

void setup() {
  pinMode(LED, OUTPUT);
}

void loop() {
  digitalWrite(LED, HIGH);
  delay(500);
  digitalWrite(LED, LOW);
  delay(500);
}

const int TRIG = 9;
const int ECHO = 10;

void setup() {
  Serial.begin(9600);
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
}

void loop() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  long us = pulseIn(ECHO, HIGH, 30000);
  float cm = us * 0.0343 / 2;

  Serial.println(cm);
  delay(200);
}

#include <DHT.h>

DHT dht(2, DHT11);

void setup() {
  Serial.begin(9600);
  dht.begin();
}

void loop() {
  float temp = dht.readTemperature();
  float hum  = dht.readHumidity();

  if (isnan(temp) || isnan(hum)) {
    Serial.println("Read error");
  } else {
    Serial.print("Temp: ");
    Serial.print(temp);
    Serial.print(" C  Hum: ");
    Serial.print(hum);
    Serial.println(" %");
  }
  delay(2000);
}

const int LDR = A0;
const int RELE = 7;
const int UMBRAL = 400;  // adjust for your sensor

void setup() {
  pinMode(RELE, OUTPUT);
  digitalWrite(RELE, HIGH);  // off (module is active-LOW)
}

void loop() {
  int luz = analogRead(LDR);

  if (luz < UMBRAL) {
    digitalWrite(RELE, LOW);   // dark: turn on
  } else {
    digitalWrite(RELE, HIGH);  // bright: turn off
  }
  delay(500);
}

#include <WiFi.h>
#include <WebServer.h>

const char* SSID = "YOUR_WIFI";
const char* CLAVE = "YOUR_PASSWORD";
const int LED = 2;

WebServer server(80);

void pagina() {
  server.send(200, "text/html",
    "<a href='/on'>Turn on</a> | <a href='/off'>Turn off</a>");
}

void setup() {
  Serial.begin(115200);
  pinMode(LED, OUTPUT);
  WiFi.begin(SSID, CLAVE);
  while (WiFi.status() != WL_CONNECTED) delay(300);
  Serial.println(WiFi.localIP());  // type this IP in your phone's browser

  server.on("/", pagina);
  server.on("/on",  []() { digitalWrite(LED, HIGH); pagina(); });
  server.on("/off", []() { digitalWrite(LED, LOW);  pagina(); });
  server.begin();
}

void loop() {
  server.handleClient();
}

import serial

with serial.Serial("COM3", 9600, timeout=1) as arduino:
    while True:
        linea = arduino.readline().decode().strip()
        if linea:
            print("Distance:", linea, "cm")