python设计模式

 

解释器模式

多用于DSL，领域专用语言，

from pyparsing import Word, OneOrMore, Optional, Group, Suppress, alphanums

 word = Word(alphanums)
 command = Group(OneOrMore(word))
 token = Suppress("->")
 device = Group(OneOrMore(word))
 argument = Group(OneOrMore(word))
 event = command + token + device + Optional(token + argument)

上面的event可以用

event.parseString(t)

解析出t

'open -> gate'  或者

'increase -> boiler temperature -> 5 degrees'

　并从中提取出open，gate用于自定义的操作。　

 

观察者模式

一个对象的属性的改变可以同时通知观察者，定义观察者HexFormatter

class HexFormatter:
    def notify(self, publisher):
        print("{}: '{}' has now hex data = {}".format(type(self).__name__, publisher.name, hex(publisher.data)))　

　观察对象

class Publisher:
    def __init__(self):
        self.observers = []
    #添加观察者
    def add(self, observer):
        if observer not in self.observers:
            self.observers.append(observer)
        else:
            print('Failed to add: {}'.format(observer))

    def remove(self, observer):
        try:
            self.observers.remove(observer)
        except ValueError:
            print('Failed to remove: {}'.format(observer))

    def notify(self):
        [o.notify(self) for o in self.observers]

class DefaultFormatter(Publisher):
    def __init__(self, name):
        Publisher.__init__(self)
        self.name = name
        self._data = 0

    def __str__(self):
        return "{}: '{}' has data = {}".format(type(self).__name__, self.name, self._data)
    #以object.data方式访问变量
    @property
    def data(self):
        return self._data
    #改变data值，最后通知观察者
    @data.setter
    def data(self, new_value):
        try:
            self._data = int(new_value)
        except ValueError as e:
            print('Error: {}'.format(e))
        else:
            self.notify()

　　

　

 

适配器模式

class Adapter:
    def __init__(self,obj,adapter_method):
        self.obj = obj
        #add obj attr
        #var = vars(obj)
        #self.__dict__.update(var)
        self.__dict__.update(adapter_method)

    def __str__(self):
        return str(self.obj)