阅读OReilly.Web.Scraping.with.Python.2015.6笔记---Crawl
1.函数调用它自身，这样就形成了一个循环，一环套一环：
from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
pages = set()
def getLinks(pageUrl):
global pages
html = urlopen("http://en.wikipedia.org"+pageUrl)
bsObj = BeautifulSoup(html,"lxml")
try:
print(bsObj.h1.get_text())
print(bsObj.find(id ="mw-content-text").findAll("p")[0]) //找到网页中 id=mw-content-text,然后在这个基础上查找"p"这个标签的内容 [0]则代表选择第0个
print(bsObj.find(id="ca-edit").find("span").find("a").attrs['href']) //找到id=ca-edit里面的span标签里面的a标签里面的href的值
except AttributeError:
print("This page is missing something! No worries though!")
for link in bsObj.findAll("a", href=re.compile("^(/wiki/)")):
if 'href' in link.attrs:
if link.attrs['href'] not in pages:
#We have encountered a new page
newPage = link.attrs['href']
print(newPage)
pages.add(newPage)
getLinks(newPage)
getLinks("")
2.对网址进行处理，通过"/"对网址中的字符进行分割
def splitAddress(address):
addressParts = address.replace("http://", "").split("/")
return addressParts
addr = splitAddress("https://hao.360.cn/?a1004")
print(addr)
运行结果为：
runfile('C:/Users/user/Desktop/chensimin.py', wdir='C:/Users/user/Desktop')
['https:', '', 'hao.360.cn', '?a1004'] //两个//之间没有内容，所用用''表示
def splitAddress(address):
addressParts = address.replace("http://", "").split("/")
return addressParts
addr = splitAddress("http://www.autohome.com.cn/wuhan/#pvareaid=100519")
print(addr)
运行结果为：
runfile('C:/Users/user/Desktop/chensimin.py', wdir='C:/Users/user/Desktop')
['www.autohome.com.cn', 'wuhan', '#pvareaid=100519']
3.抓取网站的内部链接
from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
#Retrieves a list of all Internal links found on a page
def getInternalLinks(bsObj, includeUrl):
internalLinks = []
#Finds all links that begin with a "/"
for link in bsObj.findAll("a", href=re.compile("^(/|.*"+includeUrl+")")):
if link.attrs['href'] is not None:
if link.attrs['href'] not in internalLinks:
internalLinks.append(link.attrs['href'])
return internalLinks
startingPage = "http://oreilly.com"
html = urlopen(startingPage)
bsObj = BeautifulSoup(html,"lxml")
def splitAddress(address):
addressParts = address.replace("http://", "").split("/")
return addressParts
internalLinks = getInternalLinks(bsObj, splitAddress(startingPage)[0])
print(internalLinks)
运行结果为（此页面内的所有内部链接）：
runfile('C:/Users/user/Desktop/untitled112.py', wdir='C:/Users/user/Desktop')
['https://www.oreilly.com', 'http://www.oreilly.com/ideas',
'https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170601+nav',
'http://www.oreilly.com/conferences/', 'http://shop.oreilly.com/', 'http://members.oreilly.com', '/topics/ai', '/topics/business',
'/topics/data', '/topics/design', '/topics/economy', '/topics/operations', '/topics/security', '/topics/software-architecture', '/topics/software-engineering',
'/topics/web-programming', 'https://www.oreilly.com/topics',
'https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170505+homepage+get+started+now',
'https://www.safaribooksonline.com/accounts/login/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170203+homepage+sign+in',
'https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+get+started+now',
'https://www.safaribooksonline.com/public/free-trial/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+start+free+trial',
'https://www.safaribooksonline.com/accounts/login/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170710+homepage+sign+in',
'https://www.safaribooksonline.com/live-training/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170201+homepage+take+a+live+online+course',
'https://www.safaribooksonline.com/learning-paths/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170201+homepage+follow+a+path',
'https://www.safaribooksonline.com/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170505+homepage+unlimited+access', 'http://www.oreilly.com/live-training/?view=grid',
'https://www.safaribooksonline.com/your-experience/?utm_medium=content&utm_source=oreilly.com&utm_campaign=lgen&utm_content=20170201+homepage+safari+platform',
'https://www.oreilly.com/ideas/8-data-trends-on-our-radar-for-2017?utm_medium=referral&utm_source=oreilly.com&utm_campaign=lgen&utm_content=link+2017+trends',
'https://www.oreilly.com/ideas?utm_medium=referral&utm_source=oreilly.com&utm_campaign=lgen&utm_content=link+read+latest+articles', 'http://www.oreilly.com/about/',
'http://www.oreilly.com/work-with-us.html', 'http://www.oreilly.com/careers/', 'http://shop.oreilly.com/category/customer-service.do', 'http://www.oreilly.com/about/contact.html',
'http://www.oreilly.com/emails/newsletters/', 'http://www.oreilly.com/terms/', 'http://www.oreilly.com/privacy.html', 'http://www.oreilly.com/about/editorial_independence.html']
4.抓取网站的外部链接
from urllib.request import urlopen
from bs4 import BeautifulSoup
import re
#Retrieves a list of all external links found on a page
def getExternalLinks(bsObj, excludeUrl):
externalLinks = []
#Finds all links that start with "http" or "www" that do
#not contain the current URL
for link in bsObj.findAll("a",
href=re.compile("^(http|www)((?!"+excludeUrl+").)*$")):
if link.attrs['href'] is not None:
if link.attrs['href'] not in externalLinks:
externalLinks.append(link.attrs['href'])
return externalLinks
startingPage = "http://oreilly.com"
html = urlopen(startingPage)
bsObj = BeautifulSoup(html,"lxml")
def splitAddress(address):
addressParts = address.replace("http://", "").split("/")
return addressParts
print(splitAddress(startingPage))
print(splitAddress(startingPage)[0])
externalLinks = getExternalLinks(bsObj,splitAddress(startingPage)[0])
print(externalLinks)
运行结果为：
runfile('C:/Users/user/Desktop/untitled112.py', wdir='C:/Users/user/Desktop')
['oreilly.com']
oreilly.com
['https://cdn.oreillystatic.com/pdf/oreilly_high_performance_organizations_whitepaper.pdf', 'http://twitter.com/oreillymedia', 'http://fb.co/OReilly', 'https://www.linkedin.com/company/oreilly-media', 'https://www.youtube.com/user/OreillyMedia']