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 Awake() {
p[1] = 5;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

public p as Vector2

def Awake():
p[1] = 5