设计要点

适配器模式中主要有三个角色，在设计适配器模式时要找到并区分这些角色：
1 目标：即你期望的目标接口，要转换成的接口
2 源对象：即要被转换的角色，要把谁转换成目标角色
3 适配器：适配器模式的核心角色，负责把源对象转换和包装成目标对象

实战应用

下面为电子阅读器的项目，研发之初只支持TXT和EPUB格式的电子书，但是上线半年后又希望可以找支持pdf格式，而pdf需要使用第三方库，而第三方库和之前两类的接口并不相同，这时需要对pdf的解析库进行适配。

class Page:
    '''电子书一页的内容'''
    def __init__(self,pageNum):
        self.__pageNum = pageNum

    def getContent(self):
        return "第" + str(self.__pageNum) + "页的内容"

class Catalogue:
    '''目录结构'''
    def __init__(self,title):
        self.__title = title
        self.__chapters = []
        self.setChapter("第一章")
        self.setChapter("第二章")

    def setChapter(self,title):
        self.__chapters.append(title)

    def showInfo(self):
        print("标题"+ self.__title)
        for chapter in self.__chapters:
            print(chapter)

class IBook:
    '''电子书文档的接口类'''
    def parseFile(self,filePath):
        pass

    def getCatelogue(self):
        pass

    def getPageCount(self):
        pass

    def getPage(self,pageNum):
        pass

class TxtBook(IBook):
    '''txt解析类'''
    def parseFile(self,filePath):
        '''模拟文档的解析'''
        print(filePath + "文件解析成功")
        self.__pageCount = 500
        return True

    def getCatelogue(self):
        return Catalogue("TXT电子书")

    def getPageCount(self):
        return self.__pageCount

    def getPage(self,pageNum):
        return Page(pageNum)

class EpubBook(IBook):
    '''TXT解析类'''
    def parseFile(self,filePath):
        print(filePath+"文件解析成功")
        self.__pageCount = 800
        return True

    def getCatelogue(self):
        return Catalogue("Epub电子书")

    def getPageCount(self):
        return self.__pageCount

    def getPage(self,pageNum):
        return Page(pageNum)

class Outline:
    '''第三方PDF解析库的目录类'''
    pass

class PdfPage:
    '''PDF页'''
    def __init__(self,pageNum):
        self.__pageNum = pageNum

    def getPageNum(self):
        return self.__pageNum

class ThirdPdf:
    '''第三方PDF解析库'''
    def __init__(self):
        self.__pageSize = 0

    def open(self,filePath):
        print("第三方解析PDF文件" + filePath)
        self.__pageSize = 1000
        return True

    def getOutline(self):
        return Outline()

    def pageSize(self):
        return self.__pageSize

    def page(self,index):
        return PdfPage(index)

class PdfAdapterBook(ThirdPdf,IBook):
    '''txt解析类'''

    def parseFile(self,filePath):
        rtn = super().open(filePath)
        if(rtn):
            print(filePath + "文件解析成功")
        return rtn

    def getCatelogue(self):
        outline = super().getOutline()
        print("将Outline结构目录转换成Catelogue结构的目录")
        return Catalogue("PDF电子书")

    def getPageCount(self):
        return super().pageSize()

    def getPage(self,pageNum):
        page = self.page(pageNum)
        print("将PdfPage的面向对象转换成Page的对象")
        return Page(page.getPageNum())

import os
class Reader:
    '''阅读器'''
    def __init__(self,name):
        self.__name = name
        self.__filePath = ''
        self.__curBook = None
        self.__curPageNum = -1

    def __initBook(self,filePath):
        self.__filePath = filePath
        extName = os.path.splitext(filePath)[1]
        if(extName.lower()==".epub"):
            self.__curBook = EpubBook()
        elif(extName.lower()==".txt"):
            self.__curBook = TxtBook()
        elif(extName.lower()==".pdf"):
            self.__curBook = PdfAdapterBook()
        else:
            self.__curBook = None

    def openFile(self,filePath):
        self.__initBook(filePath)
        if(self.__curBook is not None):
            rtn = self.__curBook.parseFile(filePath)
            if(rtn):
                self.__curPageNum = 1
            return rtn
        return False

    def closeFile(self):
        print("关闭"+self.__filePath+"文件")
        return True

    def showCatalogue(self):
        catalogue = self.__curBook.getCatelogue()
        catalogue.showInfo()

    def prePage(self):
        return self.gotoPage(self.__curPageNum - 1)

    def nextPage(self):
        return self.gotoPage(self.__curPageNum + 1)

    def gotoPage(self,pageNum):
        if(pageNum < 1 or pageNum > self.__curBook.getPageCount()):
            return None

        self.__curPageNum = pageNum
        print("显示器"+str(self.__curPageNum)+"页")
        page = self.__curBook.getPage(self.__curPageNum)
        page.getContent()
        return page
'''测试代码'''
def testReader():
    reader = Reader("阅读器")
    if(not reader.openFile("平凡的世界.txt")):
        return
    reader.showCatalogue()
    reader.gotoPage(1)
    reader.nextPage()
    reader.closeFile()
    print()

    if(not reader.openFile("平凡的世界.epub")):
        return
    reader.showCatalogue()
    reader.gotoPage(5)
    reader.nextPage()
    reader.closeFile()
    print()

    if(not reader.openFile("平凡的世界.pdf")):
        return
    reader.showCatalogue()
    reader.gotoPage(10)
    reader.nextPage()
    reader.closeFile()

testReader()