old_contents: #! /usr/bin/env python3.4
  
  
  from urllib.request import urlopen
  from bs4 import BeautifulSoup
  
  ## generate page url
  
  def generatePageUrl(subTitle,pageNum):
  	pageUrlList = []
  	for i in range(1,pageNum+1):
  		pageUrlList.append('http://www.allitebooks.com/'+subTitle+'/page/'+str(i))
  	return pageUrlList
  
  
  def getBookUrlInThisPage(url):
  	try:
  		html = urlopen(url)
  	except HTTPError as e:
  		return None
  	try:
  		bsObj = BeautifulSoup(html)
  		linkList = bsObj.find('main').findAll('a',{'rel':'bookmark'})
  	except AttributeError as e:
  		return None
  		
  	bookUrlListInThisPage= []
  	for link in linkList[::2]:
  		if 'href' in link.attrs:
  			bookUrlListInThisPage.append(link.attrs['href'])
  	return bookUrlListInThisPage
  
  def getPdfUrl(bookUrl):
  	try:
  		html = urlopen(bookUrl)
  	except HTTPError as e:
  		return None
  	try:
  		bsObj = BeautifulSoup(html.read())
  		pdfUrl = bsObj.find("a",{"target":"_blank"}).attrs['href']
  	except AttributeError as e:
  		return None
  	return pdfUrl    
  	
  	
  if __name__ == '__main__':
  	
  	pageNum = 61
  	subTitle = 'networking-cloud-computing'
  
  	bookUrlList = []
  	pageUrlList = generatePageUrl(subTitle,pageNum)
  		
  	for pageUrl in pageUrlList:
  		bookUrlList.extend(getBookUrlInThisPage(pageUrl))
  	for bookUrl in bookUrlList:
  		print(getPdfUrl(bookUrl))
  		
  		
  		
  
  
new_contents: #! /usr/bin/env python3.4
  
  
  from urllib.request import urlopen
  from bs4 import BeautifulSoup
  
  ## generate page url
  
  def generatePageUrl(subTitle,pageNum):
  	pageUrlList = []
  	for i in range(1,pageNum+1):
  		pageUrlList.append('http://www.allitebooks.com'+subTitle+'/page/'+str(i))
  	return pageUrlList
  
  
  def getBookUrlInThisPage(url):
  	try:
  		html = urlopen(url)
  	except HTTPError as e:
  		return None
  	try:
  		bsObj = BeautifulSoup(html)
  		linkList = bsObj.find('main').findAll('a',{'rel':'bookmark'})
  	except AttributeError as e:
  		return None
  		
  	bookUrlListInThisPage= []
  	for link in linkList[::2]:
  		if 'href' in link.attrs:
  			bookUrlListInThisPage.append(link.attrs['href'])
  	return bookUrlListInThisPage
  
  def getPdfUrl(bookUrl):
  	try:
  		html = urlopen(bookUrl)
  	except HTTPError as e:
  		return None
  	try:
  		bsObj = BeautifulSoup(html.read())
  		pdfUrl = bsObj.find("a",{"target":"_blank"}).attrs['href']
  	except AttributeError as e:
  		return None
  	return pdfUrl    
  	
  	
  if __name__ == '__main__':
  	
  	pageNum = 2
  	subTitle = ''
  
  	bookUrlList = []
  	pageUrlList = generatePageUrl(subTitle,pageNum)
  		
  	for pageUrl in pageUrlList:
  		bookUrlList.extend(getBookUrlInThisPage(pageUrl))
  	for bookUrl in bookUrlList:
  		print(getPdfUrl(bookUrl))
  		
  		
  		
  
  
subject: change default download link to main page, 2 pages