var curve : AnimationCurve = AnimationCurve.Linear (0, 0, 5, 5);
// Extract the time from the first keyframe of a curve
Debug.Log(curve[0].time);

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    public AnimationCurve curve = AnimationCurve.Linear(0, 0, 5, 5);
    void Example() {
        Debug.Log(curve[0].time);
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    public curve as AnimationCurve = AnimationCurve.Linear(0, 0, 5, 5)

    def Example():
        Debug.Log(curve[0].time)