爬虫笔记二
Posted _慕
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了爬虫笔记二相关的知识，希望对你有一定的参考价值。
一、BeautifulSoup模块
BeautifulSoup模块，该模块用于接收一个html或XML字符串，然后将其进行格式化，之后便可以使用它提供的方法进行快速查找指定元素，从而使得在HTML或XML中查找指定元素变得简单。
安装：
pip3 install beautifulsoup4 pip3 install lxml
使用示例：
from bs4 import BeautifulSoup html_doc = """ <html><head><title>The Dormouse\'s story</title></head> <body> asdf <div class="title"> <b>The Dormouse\'s story总共</b> <h1>f</h1> </div> <div class="story">Once upon a time there were three little sisters; and their names were <a class="sister0" id="link1">Els<span>f</span>ie</a>, <a href="http://example.com/lacie" class="sister" id="link2">Lacie</a> and <a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>; and they lived at the bottom of a well.</div> ad<br/>sf <p class="story">...</p> </body> </html> """ # soup = BeautifulSoup(html_doc,\'html.parser\') # 内置的parser soup = BeautifulSoup(html_doc, features="lxml") # 找到第一个a标签 tag1 = soup.find(name=\'a\') # 找到所有的a标签 tag2 = soup.find_all(name=\'a\') # 找到id＝link2的标签 类似css选择器 tag3 = soup.select(\'#link2\')
1. name 标签名称
soup = BeautifulSoup(html_doc, features="lxml") tag = soup.find(\'a\') name = tag.name # 获取标签名称 print(name) tag.name = \'span\' # 把soup中的a标签改成span标签 print(soup)
2. attr，标签属性
soup = BeautifulSoup(html_doc, features="lxml")
tag = soup.find(\'a\')
attrs = tag.attrs # 获取第一个a标签中含有的属性
print(attrs)
tag.attrs = {\'ik\':123} # 给找到的第一个a标签设置属性
tag.attrs[\'id\'] = \'iiiii\' # 给找到的第一个a标签设置属性
print(soup)
3.children,所有子标签
soup = BeautifulSoup(html_doc, features="lxml") body = soup.find(\'body\') v = body.children
4. children 所有的子子孙孙标签
soup = BeautifulSoup(html_doc, features="lxml")
body = soup.find(\'body\') # 先找到body标签
v = body.descendants # 找到body标签里所有的子孙标签
# v是一个生成器，需要循环遍历出来
for i in v:
print(i,end=\' \')
5. clear,将标签的所有子标签全部清空（保留外层标签名）
soup = BeautifulSoup(html_doc, features="lxml") tag = soup.find(\'body\') tag.clear() print(soup)
6. decompose,递归的删除所有的标签（包括外层标签）
soup = BeautifulSoup(html_doc, features="lxml") body = soup.find(\'body\') body.decompose() print(soup)
7. extract,递归的删除所有的标签，并获取删除的标签
soup = BeautifulSoup(html_doc, features="lxml") body = soup.find(\'body\') v = body.extract() print(soup)
8. decode,转换为字符串（含当前标签）；decode_contents（不含当前标签）
soup = BeautifulSoup(html_doc, features="lxml") body = soup.find(\'body\') # v = body.decode() v = body.decode_contents() print(v,type(v))
9. encode,转换为字节（含当前标签）；encode_contents（不含当前标签）
soup = BeautifulSoup(html_doc, features="lxml") body = soup.find(\'body\') # v = body.encode() v = body.encode_contents() print(v,type(v))
10. find,获取匹配的第一个标签
soup = BeautifulSoup(html_doc, features="lxml")
# 找到第一个a标签
tag = soup.find(\'a\')
print(tag)
# 找到属性中有class="sister" 文本内容为Lacie 符合要求的第一个a标签
tag = soup.find(name=\'a\', attrs={\'class\': \'sister\'}, recursive=True, text=\'Lacie\')
# tag = soup.find(name=\'a\', class_=\'sister\', recursive=True, text=\'Lacie\')
print(tag)
11. find_all,获取匹配的所有标签
soup = BeautifulSoup(html_doc, features="lxml")
# 找到所有a标签
tags = soup.find_all(\'a\')
print(tags)
# 找到所有的a标签后取第一个
tags = soup.find_all(\'a\',limit=1)
print(tags)
# 找到所有属性class="sister" 文本内容为Lacie 的a标签
tags = soup.find_all(name=\'a\', attrs={\'class\': \'sister\'}, recursive=True, text=\'Lacie\')
# tags = soup.find(name=\'a\', class_=\'sister\', recursive=True, text=\'Lacie\')
print(tags)
# ####### 列表 #######
v = soup.find_all(name=[\'a\',\'div\'])
print(v)
v = soup.find_all(class_=[\'sister0\', \'sister\'])
print(v)
v = soup.find_all(text=[\'Tillie\'])
print(v, type(v[0]))
v = soup.find_all(id=[\'link1\',\'link2\'])
print(v)
v = soup.find_all(href=[\'link1\',\'link2\'])
print(v)
# ####### 正则 #######
import re
# rep = re.compile(\'p\')
rep = re.compile(\'^p\')
v = soup.find_all(name=rep)
print(v)
rep = re.compile(\'sister.*\')
v = soup.find_all(class_=rep)
print(v)
rep = re.compile(\'http://www.oldboy.com/static/.*\')
v = soup.find_all(href=rep)
print(v)
# ####### 方法筛选 #######
def func(tag):
return tag.has_attr(\'class\') and tag.has_attr(\'id\')
v = soup.find_all(name=func)
print(v)
## get,获取标签属性
tag = soup.find(\'a\')
v = tag.get(\'id\')
print(v)
12. has_attr,检查标签是否具有该属性
soup = BeautifulSoup(html_doc, features="lxml") tag = soup.find(\'a\') v = tag.has_attr(\'id\') print(v)
13. get_text,获取标签内部文本内容
soup = BeautifulSoup(html_doc, features="lxml") tag = soup.find(\'a\') v = tag.get_text() print(v)
14. index,检查标签在某标签中的索引位置
soup = BeautifulSoup(html_doc, features="lxml")
tag = soup.find(\'body\')
v = tag.index(tag.find(\'div\'))
print(v)
tag = soup.find(\'body\')
for i,v in enumerate(tag):
print(i,v)
15. is_empty_element,是否是空标签(是否可以是空)或者自闭合标签，判断是否是如下标签：\'br\' , \'hr\', \'input\', \'img\', \'meta\',\'spacer\', \'link\', \'frame\', \'base\'
soup = BeautifulSoup(html_doc, features="lxml") tag = soup.find(\'br\') v = tag.is_empty_element print(v)
16. 当前的关联标签
soup = BeautifulSoup(html_doc, features="lxml") # soup.next # soup.next_element # soup.next_elements # soup.next_sibling # soup.next_siblings # # tag.previous # tag.previous_element # tag.previous_elements # tag.previous_sibling # tag.previous_siblings # # tag.parent # tag.parents
17. 查找某标签的关联标签
# tag.find_next(...) # tag.find_all_next(...) # tag.find_next_sibling(...) # tag.find_next_siblings(...) # tag.find_previous(...) # tag.find_all_previous(...) # tag.find_previous_sibling(...) # tag.find_previous_siblings(...) # tag.find_parent(...) # tag.find_parents(...) # 参数同find_all
18. select,select_one, CSS选择器
soup.select("title")
soup.select("p nth-of-type(3)")
soup.select("body a")
soup.select("html head title")
tag = soup.select("span,a")
soup.select("head > title")
soup.select("p > a")
soup.select("p > a:nth-of-type(2)")
soup.select("p > #link1")
soup.select("body > a")
soup.select("#link1 ~ .sister")
soup.select("#link1 + .sister")
soup.select(".sister")
soup.select("[class~=sister]")
soup.select("#link1")
soup.select("a#link2")
soup.select(\'a[href]\')
soup.select(\'a[href="http://example.com/elsie"]\')
soup.select(\'a[href^="http://example.com/"]\')
soup.select(\'a[href$="tillie"]\')
soup.select(\'a[href*=".com/el"]\')
from bs4.element import Tag
def default_candidate_generator(tag):
for child in tag.descendants:
if not isinstance(child, Tag):
continue
if not child.has_attr(\'href\'):
continue
yield child
tags = soup.find(\'body\').select("a", _candidate_generator=default_candidate_generator)
print(type(tags), tags)
from bs4.element import Tag
def default_candidate_generator(tag):
for child in tag.descendants:
if not isinstance(child, Tag):
continue
if not child.has_attr(\'href\'):
continue
yield child
tags = soup.find(\'body\').select("a", _candidate_generator=default_candidate_generator, limit=1)
print(type(tags), tags)
19. 标签的内容
# tag = soup.find(\'span\') # print(tag.string) # 获取 # tag.string = \'new content\' # 设置 # print(soup) # tag = soup.find(\'body\') # print(tag.string) # tag.string = \'xxx\' # print(soup) # tag = soup.find(\'body\') # v = tag.stripped_strings # 递归内部获取所有标签的文本 # print(v)
20.append在当前标签内部追加一个标签
soup = BeautifulSoup(html_doc, features="lxml")
tag = soup.find(\'body\')
tag.append(soup.find(\'a\'))
print(soup)
from bs4.element import Tag
obj = Tag(name=\'i\',attrs={\'id\': \'it\'})
obj.string = \'我是一个新来的\'
tag = soup.find(\'body\')
tag.append(obj)
print(soup)
21.insert在当前标签内部指定位置插入一个标签
# from bs4.element import Tag
# obj = Tag(name=\'i\', attrs={\'id\': \'it\'})
# obj.string = \'我是一个新来的\'
# tag = soup.find(\'body\')
# tag.insert(2, obj)
# print(soup)
22. insert_after,insert_before 在当前标签后面或前面插入
# from bs4.element import Tag
# obj = Tag(name=\'i\', attrs={\'id\': \'it\'})
# obj.string = \'我是一个新来的\'
# tag = soup.find(\'body\')
# # tag.insert_before(obj)
# tag.insert_after(obj)
# print(soup)
23. replace_with 在当前标签替换为指定标签
# from bs4.element import Tag
# obj = Tag(name=\'i\', attrs={\'id\': \'it\'})
# obj.string = \'我是一个新来的\'
# tag = soup.find(\'div\')
# tag.replace_with(obj)
# print(soup)
24. 创建标签之间的关系
# tag = soup.find(\'div\') # a = soup.find(\'a\') # tag.setup(previous_sibling=a) # print(tag.previous_sibling)
25. wrap，将指定标签把当前标签包裹起来
# from bs4.element import Tag
# obj1 = Tag(name=\'div\', attrs={\'id\': \'it\'})
# obj1.string = \'我是一个新来的\'
#
# tag = soup.find(\'a\')
# v = tag.wrap(obj1)
# print(soup)
# tag = soup.find(\'a\')
# v = tag.wrap(soup.find(\'p\'))
# print(soup)
26. unwrap，去掉当前标签，将保留其包裹的标签
# tag = soup.find(\'a\') # v = tag.unwrap() # print(soup)
转载：武沛齐
二、爬虫性能相关
详细：性能相关
import socket import select class Request(object): def __init__(self, sock, info): self.sock = sock self.info = info # 调用sock内部的fileno方法 def fileno(self): return self.sock.fileno() class AsyncRequest(object): def __init__(self): self.sock_list = [] self.conns = [] def add_request(self, req_info): """ 创建请求 req_info: {\'host\': \'www.baidu.com\', \'port\': 80, \'path\': \'/\'}, :return: """ sock = socket.socket() sock.setblocking(False) try: sock.connect((req_info[\'host\'], req_info[\'port\'])) except BlockingIOError as e: pass obj = Request(sock, req_info) self.sock_list.append(obj) self.conns.append(obj) def run(self): """ 开始事件循环,检测：连接成功？数据是否返回？ :return: """ while True: # select.select([socket对象,]) # 可是任何对象，对象一定要fileno方法 # 对象.fileno() # select.select([request对象,]) rlist, wlist, elist = select.select(self.sock_list, self.conns, [], 0.05) # wlist,是否连接成功 for obj in wlist: # 检查obj:request对象 # socket, {\'host\': \'www.baidu.com\', \'port\': 80, \'path\': \'/\'}, data = "GET %s http/1.1\\r\\nhost:%s\\r\\n\\r\\n" % (obj.info[\'path\'], obj.info[\'host\']) obj.sock.send(data.encode(\'utf-8\')) self.conns.remove(obj) # rlist 数据返回，接收到数据 for obj in rlist: response = obj.sock.recv(8096) obj.info[\'callback\'](response) self.sock_list.remove(obj) # self.sock_list为空时，表明所有请求已经返回 if not self.sock_list: break # 相应网址定制的回调函数 def done1(response): print(response) # 相应网址定制的回调函数 def done2(response): print(response) url_list = [ {\'host\': \'www.baidu.com\', \'port\': 80, \'path\': \'/\', \'callback\': done1}, {\'host\': \'www.cnblogs.com\', \'port\': 80, \'path\': \'/index.html\', \'callback\': done2}, {\'host\': \'www.bing.com\', \'port\': 80, \'path\': \'/\', \'callback\': done2}, ] asyncRequest = AsyncRequest() for item in url_list: asyncRequest.add_request(item) asyncRequest.run()
import socket import select ############### HTTP请求本质 阻塞 """ sk = socket.socket() # 连接 sk.connect((\'www.baidu.com\',80)) # IO阻塞 print(\'连接成功\') # 发送消息 sk.send(b\'GET / HTTP/1.0\\r\\nHost:www.baidu.com\\r\\n\\r\\n\') # 等待服务端响应 data = sk.recv(8096) # IO阻塞 print(data) #关闭连接 sk.close() """ ############### HTTP请求本质 非阻塞 # sk = socket.socket() # sk.setblocking(False) # # try: # # 连接 # sk.connect((\'www.baidu.com\',80)) # IO阻塞 # print(\'连接成功\') # except BlockingIOError as e: # print(e) # # # 发送消息 # sk.send(b\'GET / HTTP/1.0\\r\\nHost:www.baidu.com\\r\\n\\r\\n\') # # # 等待服务端响应 # data = sk.recv(8096) # IO阻塞 # print(data) # # #关闭连接 # sk.close() #########################
url_list = [ \'http://www.cnblogs.com/wupeiqi/articles/6229292.html\', \'http://www.baidu.com\', \'http://www.xiaohuar.com\', ] import requests # 1. 穿行(6s，1个) # for url in url_list: # response = requests.get(url) # print(response.content) # 2. 线程，进程(3s，三个) # from concurrent.futures import ThreadPoolExecutor,ProcessPoolExecutor # # def tast(url): # response = requests.get(url) # print(response.content) # # pool = ThreadPoolExecutor(10) # # pool = ProcessPoolExecutor(10) # for url in url_list: # # requests.get(url) # pool.submit(tast,url) # 线程池中获取一个线程，执行task函数 # pool.shutdown(wait=True) # 3. 异步非阻塞 # 【异步】，回调(请求发出去后就不管了，然后去干别的事情，等执行完后回调函数告诉我一下，) # 【非阻塞】，不等，socket， # 阻塞： client = socket();client.connet(ip,端口) # 非阻塞：client = socket(); client.setblocking(False); client.connet(ip,端口) # 【协程】和异步非阻塞没有关系，协程是人为的先控制这执行一会儿然后再那儿执行一会儿 #连接；发送数据；接受数据 from twisted.web.client import getPage, defer from twisted.internet import reactor def all_done(arg): reactor.stop() def callback(contents): print(contents) deferred_list = [] url_list = [\'http://www.bing.com\', \'http://www.baidu.com\', ] for url in url_list: deferred = getPage(bytes(url, encoding=\'utf8\')) # requests deferred.addCallback(callback) deferred_list.append(deferred) dlist = defer.DeferredList(deferred_list) dlist.addCallback(all_done) reactor.run()
以上是关于爬虫笔记二的主要内容，如果未能解决你的问题，请参考以下文章
爬虫学习笔记（十八）—— 点触验证码：超级鹰12306自动登录