Application.isPlaying

Description

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

Returns true in the Unity editor when in play mode.

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

using UnityEngine;
using System.Collections;

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