Does the object exist?

	// 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

public class Example(MonoBehaviour):

	def Example() as void:
		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

public class Example(MonoBehaviour):

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