Application.isEditor
static var isEditor: bool;
static bool isEditor;
static isEditor as bool
Description

Are we running inside the Unity editor? (Read Only)

Returns true if the game is being run from the Unity editor; false if run from any deployment target.
	if (Application.isEditor) {
		print("We are running this from inside of the editor!");
	}
using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        if (Application.isEditor)
            print("We are running this from inside of the editor!");
        
    }
}
import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		if Application.isEditor:
			print('We are running this from inside of the editor!')