1. 工厂模式实现了对多个类的统一管理,简单的理解就是判断应该调用哪个类

IT虾米网

# 工厂模式 
''' 
一般情况下我们要创建一个工厂类（创造我们想创造的东西） 
''' 
  
class CarFactory:  # 工厂类 
    def create_car(self, brand): 
        if brand == "奔驰": 
            return Benz() 
        elif brand == "宝马": 
            return BMW() 
        elif brand == "比亚迪": 
            return BYD() 
        else: 
            return '未知品牌，无法创建' 
  
class Benz: 
    pass 
  
class BMW: 
    pass 
  
class BYD: 
    pass 
  
factory = CarFactory() 
c1 = factory.create_car("奔驰") 
c2 = factory.create_car("宝马") 

2. 单例模式实现了,最资源的重复利用,比如数据库的连接.

IT虾米网

import pymysql 
  
  
class Singleton(object): 
    _instance = None 
  
    def __new__(cls, name): 
        if not cls._instance: 
            cls._instance = object.__new__(cls) 
        return cls._instance 
  
  
class A(Singleton): 
    def __init__(self, name): 
        self.name = name 
        self.conn = pymysql.connect(host='127.0.0.1', user='root', password='root', database='job', 
                                    charset='utf8') 
  
  
if __name__ == '__main__': 
    a = A('apple') 
    b = A('bnana') 
    print(a, b)