Application.isPlaying
static var isPlaying: bool;
static bool isPlaying;
static isPlaying as bool
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 Example : MonoBehaviour {
    void Example() {
        if (Application.isPlaying)
            print("In player or playmode");
        
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

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