Python设计模式和pickle模块
作者:互联网
设计模式
在IT行业中设计模式总共有23种,可以分为三大类,创建型,结构型,行为型。
设计模式之单例模式。
单例模式的意思是一个类只能产生一个对象,用于节省资源。
第一种(基于classmethod)
class Mysql(object):
_instance = None
def __init__(self, ip, port):
self.ip = ip
self.port = port
@classmethod
def singleton(cls):
if not cls._instance:
cls._instance = Mysql('127.0.0.1', 3306)
return cls._instance
obj1 = Mysql.singleton()
obj2 = Mysql.singleton()
print(obj1)
print(obj2)
第二种(基于装饰器)
def singleton(cls):
# 该对象在类Mysql被装饰上singleton的时候就已经实例化完毕
_instance = cls('127.0.0.1',3306)
def inner(*args,**kwargs):
# 判断是否传入参数,传入参数表示要实例化新的,不传表示用默认的
if args or kwargs:
obj = cls(*args,**kwargs)
return obj
return _instance
return inner
@singleton
class Mysql:
def __init__(self,ip,port):
self.ip = ip
self.port = port
obj1 = Mysql()
obj2 = Mysql()
obj3 = Mysql()
print(obj1,obj2,obj3)
第三种(基于元类)
class MymetaClass(type):
def __call__(self, *args, **kwargs):
if not hasattr(self,'instance'):
self.instance = super().__call__(*args,**kwargs)
return self.instance
class Mysql(metaclass=MymetaClass):
def __init__(self,host,port):
self.host = host
self.port = port
obj = Mysql('ajdak',213)
obj1 = Mysql('asdasdas',134234)
print(obj,obj1)
第四种(基于__new__)
class Mysql(object):
_instance = None
def __init__(self,name):
self.name = name
def __new__(cls, *args, **kwargs):
if not cls._instance:
cls._instance = object.__new__(cls)
return cls._instance
obj = Mysql('egon')
obj1 = Mysql('jason')
print(id(obj),id(obj1))
第五种(基于模块)
# 单独在一个py文件中定义一个类,并实例化一个对象,之后在其他文件导入这一对象,实现单例
class Singleton(object):
def __init__(self,host,port):
self.host = host
self.port = port
singleton = Singleton('127.0.0.1',3306)
pickle模块
将该模块的目的仅仅是为了在选课系统中使用,后期会学习ORM就不会用pickle了。并且该模块只支持python 兼容性很差!!!
将对象保存到文件`
import pickle
class MyClass(object):
school = 'school'
def __init__(self, name):
self.name = name
def choose_course(self):
print('%s正在选课'%self.name)
obj = MyClass('jason')
print(obj.school)
obj.choose_course()
从文件中获取对象
with open(r'jason','rb') as f:
data = pickle.load(f)
print(data)
print(data.name)
print(data.school)
标签:__,Python,self,instance,Mysql,设计模式,pickle,port,cls 来源: https://www.cnblogs.com/zaoan1207/p/16138351.html