function Start() {
    var mesh : Mesh = GetComponent(MeshFilter).mesh;
    Debug.Log("Submeshes: " + mesh.subMeshCount);
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Start() {
        Mesh mesh = GetComponent<MeshFilter>().mesh;
        Debug.Log("Submeshes: " + mesh.subMeshCount);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Start():
        mesh as Mesh = GetComponent[of MeshFilter]().mesh
        Debug.Log(('Submeshes: ' + mesh.subMeshCount))