2019独角兽企业重金招聘Python工程师标准>>> 
1、打开oreilly free主页：
http://www.oreilly.com/programming/free/
在页面上检查元素，执行以下JS代码，获得书籍下载链接列表
$.map($('body > article:nth-child(4) > div > section > div > a'), function(e){return e.href.replace(/free/, "free/files").replace(/csp.*/, "pdf")})得到的列表如下 :
["http://www.oreilly.com/programming/free/files/open-source-in-brazil.pdf",
"http://www.oreilly.com/programming/free/files/ten-steps-to-linux-survival.pdf",
"http://www.oreilly.com/programming/free/files/open-by-design.pdf",
"http://www.oreilly.com/programming/free/files/getting-started-with-innersource.pdf",
"http://www.oreilly.com/programming/free/files/microservices-in-production.pdf",
"https://info.lightbend.com/COLL-20XX-Developing-Reactive-Microservices_Landing-Page.html?lst=OR",
"http://www.oreilly.com/programming/free/files/microservices-antipatterns-and-pitfalls.pdf",
"http://www.oreilly.com/programming/free/files/microservices-vs-service-oriented-architecture.pdf",
"http://www.oreilly.com/programming/free/files/evolving-architectures-of-fintech.pdf",
"http://www.oreilly.com/programming/free/files/software-architecture-patterns.pdf",
"http://www.oreilly.com/programming/free/files/migrating-cloud-native-application-architectures.pdf",
"http://www.oreilly.com/programming/free/files/reactive-microservices-architecture-orm.pdf"]2、编写Python代码执行下载：
第一版代码：直接使用urllib库的urlretrieve函数进行下载，得到的列表中有可能存在非法值，在循环里进行判断并跳过。
import urllib
path = "G:\\books\\auto_dowloading\\"
def downloading(books):
for book in books:
tmp = book.split("/")
if '.pdf' not in book:
continue
print "downloading %s" %(tmp[-1])
urllib.urlretrieve(book, path+tmp[-1])
print "download %s is over!" %(tmp[-1])
print "all job done"第二版代码：通过输入网址链接，爬取所有书籍的地址列表，将列表传入进程池调用下载函数进行下载。
import urllib
import os
import re
from multiprocessing import Pool
path = "G:\\books_new\\"
job =[]
def get_booklist(url):
page = urllib.urlopen(url)
html = page.read()
tmp = re.findall(r'http://.*?\.csp',html)
tmp2 = [i.replace('free','free/files').replace('csp','pdf') for i in tmp ]
job.extend(tmp2)
def download_book(url,path=path):
if '.pdf' not in url:
return
name = url.split("/")[-1]
print "downloading %s" %(name)
urllib.urlretrieve(url, path+name)
print "download %s is over!" %(name)
if __name__=='__main__':
get_booklist('http://www.oreilly.com/programming/free/')
pool=Pool()
pool.map(download_book,job)
print('The documents have been downloaded successfully !')