// check if there is a rigidbody attached to this transform

if (rigidbody) 
   Debug.Log("Rigidbody attached to this transform");

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        if (rigidbody)
            Debug.Log("Rigidbody attached to this transform");
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        if rigidbody:
            Debug.Log('Rigidbody attached to this transform')

// another way to check if a rigidbody is attached to this transform

if (rigidbody != null)
   Debug.Log("Rigidbody attached to this transform");

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        if (rigidbody != null)
            Debug.Log("Rigidbody attached to this transform");
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        if rigidbody != null:
            Debug.Log('Rigidbody attached to this transform')