Application.isPlaying

static var isPlaying : boolean

Description

Returns true when in any kind of player (Read Only).

Returns true in the Unity editor when in play mode.

JavaScript

if (Application.isPlaying) {
    print("In player or playmode");
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        if (Application.isPlaying)
            print("In player or playmode");
        
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        if Application.isPlaying:
            print('In player or playmode')