Python 工厂模式,单例模式简单理解

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

# 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.

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)

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懂得,原来世界如此简单!