Python 设计模式 简单工厂模式

    简单工厂模式，作为OO ，一个较为简单的创建者设计模式。其主要思想，通过接口或继承创建 不同的子类。

 

    现在一个DOM解析器作为父类，其中XML,SOUP 分别作为两个不同解析方式，作为子类。

   Vechicl 的创建 如下

  

#外部依赖的接口，它屏蔽了我具体使用的第三方库
class tnDomTree:
    def __init__(self,htmlStream):
        self.htmlStream = htmlStream
    
    def getLinkList(self):
        pass
    
    def getImageList(self):
        pass
    
    def elementToString(self,element):
        pass
    
    def getAttrValueOfElement(self,element,attName):
        pass

 具体子类的实现方式 

XML

from lxml.html import tostring
from lxml.html.soupparser import fromstring
class tnDomTreeWithlXml(tnDomTree):
    def __init__(self,htmlStream):
        tnDomTree.__init__(self,htmlStream)
        self._tree = fromstring(self.htmlStream)
    
    def getLinkList(self):
        list = []
        for i in self._tree.iter():
            if i.tag == 'a':
                list.append(i)
        return list
    
    def getImageList(self):
        list = []
        for i in self._tree.iter():
            if i.tag == 'img':
                list.append(i)
        return list
    
    def elementToString(self,element):
        return tostring(element)
    
    def getAttrValueOfElement(self,element,attName):
        if attName in set(element.keys()):
            return str(element.attrib[attName])
        else:
            return ""

SOAP

from BeautifulSoup import BeautifulSoup
class tnDomTreeWithSoup(tnDomTree):
    def __init__(self,htmlStream):
        tnDomTree.__init__(self,htmlStream)
        self._tree = BeautifulSoup(self.htmlStream)
    
    def getLinkList(self):
        return self._tree.findAll('a')
    
    def getImageList(self):
        return self._tree.findAll('img')
    
    def elementToString(self,element):
        return str(element)
    
    def getAttrValueOfElement(self,element,attName):
        if hasattr(element,attName):
            return str(element[attName])
        else:
            return ""

creator

#工厂模式
def createDomTree(htmlStream,type='soup'):
    if type == "soup":
        return tnDomTreeWithSoup(htmlStream)
    
    if type == "lxml":
        return tnDomTreeWithlXml(htmlStream)
    
    return None

简单的测试 ：

if __name__ == "__main__":
    s1 = '''
    <p>BEIAI</p> <p><img src="/attachment/28" alt=""></p>
    '''
    print s1
    domtree = createDomTree(s1,'soup')
    list = domtree.getImageList()
    for i in list:
        print domtree.getAttrValueOfElement(i,'src')
        print domtree.elementToString(i)

这就是一个简单的使用Python 实现的 简单工厂设计模式。