AnimationClip.length  

animation.Play();
// Wait for the animation to have finished
yield WaitForSeconds (animation.clip.length);

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    IEnumerator Example() {
        animation.Play();
        yield return new WaitForSeconds(animation.clip.length);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example() as IEnumerator:
        animation.Play()
        yield WaitForSeconds(animation.clip.length)