// Set the text of the attached Text mesh
GetComponent(TextMesh).text = "Hello World";

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        GetComponent<TextMesh>().text = "Hello World";
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        GetComponent[of TextMesh]().text = 'Hello World'