My Code is : 

public class PriceBookController {
    public PriceBookController(){
        
        Pricebook2  p = new Pricebook2();
        p.name='Lenovo Pricebook2';
        p.Description ='Pricebook with All product and Price';
        p.IsActive = true;
        insert p;

        
       List<Product2> proList = new List<Product2>(); 
        
        for(Integer i =0 ;i<10;i++){ 
            Product2 pro = new Product2();            
            pro.Name = 'Lenovo'+ i; 
                       
            proList.add(pro); 
        } 
        insert proList;
         
        Pricebook2 standardPB = [select id from Pricebook2 where isStandard=true];
        PricebookEntry standardPBE = new PricebookEntry(Pricebook2Id = standardPB.Id, Product2Id = proList[0].Id, UnitPrice = 1000, IsActive = true);
        insert standardPBE;
      
        PricebookEntry  pb = new PricebookEntry();
        pb.IsActive =true;
        pb.Pricebook2Id =p.id;
        pb.UseStandardPrice =false;   
        pb.UnitPrice =5001;
        pb.Product2Id=proList[0].Id;
        
        insert pb;

        }
           
        
        }
        
    NOTE :  It is only assign one product with standard pricebook and custom pricebook and for rest of the product they will not assign anything.