Check out example codes for "singleton pattern". It will help you in understanding the concepts better.

Code Example 1

class Singleton(object):
    __instance = None
    def __new__(cls, *args):
        if cls.__instance is None:
            cls.__instance = object.__new__(cls, *args)
        return cls.__instance

Code Example 2

class Singleton:
    __instance = None
    def __new__(cls, *args):
        if cls.__instance is None:
            cls.__instance = object.__new__(cls, *args)
        return cls.__instance

Code Example 3

using UnityEngine;

public class SingeltonObject : MonoBehaviour
{

    void Awake()
    {
        SetUpSingelton();   
    }

    private void SetUpSingelton()
    {
        if (FindObjectsOfType(GetType()).Length > 1)
        {
            Destroy(gameObject);
        }
        else
        {
            DontDestroyOnLoad(gameObject);
        }
    }
}

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