提取列表R中的第一个数字

R = [10, 'a', 20.5, True]
first_number = R[0]
print(first_number)

let R = [10, 'a', 20.5, true];
let firstNumber = R[0];
console.log(firstNumber);

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<Object> R = new ArrayList<>();
        R.add(10);
        R.add('a');
        R.add(20.5);
        R.add(true);
        
        Object firstNumber = R.get(0);
        System.out.println(firstNumber);
    }
}

using System;
using System.Collections.Generic;

class Program {
    static void Main() {
        List<object> R = new List<object> { 10, 'a', 20.5, true };
        object firstNumber = R[0];
        Console.WriteLine(firstNumber);
    }
}

R = [10, 'a', 20.5, true]
first_number = R[0]
puts first_number

<?php
$R = [10, 'a', 20.5, true];
$first_number = $R[0];
echo $first_number;
?>

if R:
    first_number = R[0]
else:
    first_number = None  # 或者抛出异常

if isinstance(R[0], (int, float)):
    first_number = R[0]
else:
    first_number = None  # 或者进行其他处理