var p : Vector2;
p[1] = 5; // the same as p.y = 5

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public Vector2 p;
    void Example() {
        p[1] = 5;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public p as Vector2

    def Example():
        p[1] = 5