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How Python uses the Beautiful Soup (BS4) library to parse HTML and XML
- 王林forward
- 2023-05-13 21:55:041759browse
1. Overview of Beautiful Soup:
Beautiful Soup supports Python libraries that extract data from HTML or XML files;
It supports the HTML parser in the Python standard library, and also supports some Third-party parser lxml.
Beautiful Soup automatically converts input documents to Unicode encoding and output documents to UTF-8 encoding.
Installation:
pip install beautifulsoup4
Optional to install the parser
pip install lxmlpip install html5lib
<!DOCTYPE html>
<html>
<head>
<meta content="text/html;charset=utf-8" http-equiv="content-type" />
<meta content="IE=Edge" http-equiv="X-UA-Compatible" />
<meta content="always" name="referrer" />
<link href="https://ss1.bdstatic.com/5eN1bjq8AAUYm2zgoY3K/r/www/cache/bdorz/baidu.min.css" rel="external nofollow" rel="stylesheet" type="text/css" />
<title>百度一下，你就知道 </title>
</head>
<body link="#0000cc">
<div id="wrapper">
<div id="head">
<div class="head_wrapper">
<div id="u1">
<a class="mnav" href="http://news.baidu.com" rel="external nofollow" name="tj_trnews">新闻 </a>
<a class="mnav" href="https://www.hao123.com" rel="external nofollow" name="tj_trhao123">hao123 </a>
<a class="mnav" href="http://map.baidu.com" rel="external nofollow" name="tj_trmap">地图 </a>
<a class="mnav" href="http://v.baidu.com" rel="external nofollow" name="tj_trvideo">视频 </a>
<a class="mnav" href="http://tieba.baidu.com" rel="external nofollow" rel="external nofollow" name="tj_trtieba">贴吧 </a>
<a class="bri" href="//www.baidu.com/more/" rel="external nofollow" name="tj_briicon" >更多产品 </a>
</div>
</div>
</div>
</div>
</body>
</html> Create a beautifulsoup4 object: from bs4 import BeautifulSoup
file = open('./aa.html', 'rb')
html = file.read()
bs = BeautifulSoup(html, "html.parser") # 缩进格式
print(bs.prettify()) # 格式化html结构
print(bs.title) #
print(bs.title.name) # 获取title标签的名称 :title
print(bs.title.string) # 获取title标签的文本内容 : 百度一下，你就知道
print(bs.head) # 获取head标签的所有内容 :
print(bs.div) # 获取第一个div标签中的所有内容 :
print(bs.div["id"]) # 获取第一个div标签的id的值 : wrapper
print(bs.a) # 获取第一个a标签中的所有内容 : <a href="http://news.baidu.com/" rel="external nofollow" target="_blank">新闻 </a>
print(bs.find_all("a")) # 获取所有的a标签中的所有内容 : [....]
print(bs.find(id="u1")) # 获取id="u1"的所有内容 :
for item in bs.find_all("a"): # 获取所有的a标签，并遍历打印a标签中的href的值 :
print(item.get("href"))
for item in bs.find_all("a"): # 获取所有的a标签，并遍历打印a标签的文本值:
print(item.get_text()) 3. The four major types of BeautifulSoup4 objects BeautifulSoup4 converts complex HTML The document is converted into a complex tree structure. Each node is a Python object. All objects can be summarized into 4 types: Tag, NavigableString, BeautifulSoup, Comment, 1, Tag: Tag## In layman's terms, #Tag is a tag in HTML, for example:
print(bs.title) # 获取title标签的所有内容 print(bs.head) # 获取head标签的所有内容 print(bs.a) # 获取第一个a标签的所有内容 print(type(bs.a))# 类型
We can use soup to add the tag name to easily obtain the content of these tags. The type of these objects is bs4.element.Tag. But note that it looks for the first matching tag in all content.
For Tag, it has
two important attributes, name and attrs:print(bs.name) # [document] #bs 对象本身比较特殊，它的 name 即为 [document]
print(bs.head.name) # head #对于其他内部标签，输出的值便为标签本身的名称
print(bs.a.attrs) # 在这里，我们把 a 标签的所有属性打印输出了出来，得到的类型是一个字典。
print(bs.a['class']) ##还可以利用get方法，传入属性的名称，二者是等价的，等价 bs.a.get('class')
bs.a['class'] = "newClass"# 可以对这些属性和内容等等进行修改
print(bs.a)
del bs.a['class'] # 还可以对这个属性进行删除
print(bs.a)
2. NavigableString: the text inside the tag
Since We have got the content of the label, so the question is, what should we do if we want to get the text inside the label? It's very simple, just use .string, for example:
print(bs.title.string) # 百度一下，你就知道 print(type(bs.title.string)) #
3. BeautifulSoup: the content of the document
The BeautifulSoup object represents the content of a document. Most of the time, it can be regarded as a Tag object, which is a special Tag. We can obtain its type, name, and attributes respectively, for example:
print(type(bs.name)) #
print(bs.name) # [document]
print(bs.attrs) # {}4. Comment: Comment
## The #Comment object is a special type of NavigableString object, and its output content does not include comment symbols.print(bs.a)
# 此时不能出现空格和换行符，a标签如下：
#
print(bs.a.string) # 新闻
print(type(bs.a.string)) #
4. Properties used to traverse the document tree
- .contents:
- Get all child nodes of Tag and return a list
print(bs.head.contents) # tag的.contents属性可以将tag的子节点以列表的方式输出:[...] print(bs.head.contents[1]) # 用列表索引来获取它的某一个元素:
- children:
- Get all child nodes of Tag and return a generator
for child in bs.body.children: print(child)
- .descendants
- : Get all descendant nodes of Tag
##.parent
: Get the parent node of Tag -
.parents : Recursively obtain all nodes of the parent element and return a generator -
.previous_sibling
: Get the current Tag's previous node, the attribute is usually a string or blank, the actual result is the comma and newline character between the current tag and the previous tag -
##.next_sibling
: Get the next node of the current Tag. The attribute is usually a string or blank. The result is the comma and newline character between the current tag and the next tag. -
.previous_siblings
: Get all the sibling nodes above the current Tag and return a generator -
.next_siblings
: Get all the sibling nodes below the current Tag , returns a generator -
.previous_element
: Gets the last parsed object (string or tag) during the parsing process, which may be the same as previous_sibling, but usually It’s different -
.next_element
: Gets the next parsed object (string or tag) during the parsing process, which may be the same as next_sibling, but usually Different -
.previous_elements
: Returns a generator that can forward access the parsed content of the document -
.next_elements
: Returns a generator that can access the parsed content of the document backwards -
.strings
: If Tag contains multiple strings, That is, there is content in the descendant nodes, you can use this to obtain, and then traverse -
.stripped_strings
: The usage is the same as strings, except that the redundant ones can be removed Blank content -
.has_attr:
Judge whether Tag contains attributes -
5. Search document tree
1. find_all(): filter
find_all(name, attrs, recursive, text, **kwargs):
find_all filter can be used in tag In the name, the attributes of the node, etc. (1) name parameter:
String filtering
: Will find content that exactly matches the stringa_list = bs.find_all("a")
print(a_list)
Regular expression Filtering: If a regular expression is passed in, BeautifulSoup4 will match the content through search()
import re
t_list = bs.find_all(re.compile("a"))
for item in t_list:
print(item)
List: If a list is passed in, BeautifulSoup4 will match the list The node matched by any element in returns
t_list = bs.find_all(["meta","link"])
for item in t_list:
print(item)
Method: Pass in a method and match based on the method.
def name_is_exists(tag):
return tag.has_attr("name")
t_list = bs.find_all(name_is_exists)
for item in t_list:
print(item)
（2）kwargs参数：
t_list = bs.find_all(id="head") # 查询id=head的Tag
t_list = bs.find_all(href=re.compile(http://news.baidu.com)) # 查询href属性包含ss1.bdstatic.com的Tag
t_list = bs.find_all(class_=True) # 查询所有包含class的Tag(注意：class在Python中属于关键字，所以加_以示区别)
for item in t_list:
print(item)（3）attrs参数：
并不是所有的属性都可以使用上面这种方式进行搜索，比如HTML的data-*属性：
t_list = bs.find_all(data-foo="value")
如果执行这段代码，将会报错。我们可以使用attrs参数，定义一个字典来搜索包含特殊属性的tag：
t_list = bs.find_all(attrs={"data-foo":"value"})
for item in t_list:
print(item)（4）text参数：
通过text参数可以搜索文档中的字符串内容，与name参数的可选值一样，text参数接受 字符串，正则表达式，列表
t_list = bs.find_all(text="hao123")
t_list = bs.find_all(text=["hao123", "地图", "贴吧"])
t_list = bs.find_all(text=re.compile("\d"))当我们搜索text中的一些特殊属性时，同样也可以传入一个方法来达到我们的目的：
def length_is_two(text):
return text and len(text) == 2
t_list = bs.find_all(text=length_is_two)（5）limit参数：
可以传入一个limit参数来限制返回的数量，当搜索出的数据量为5，而设置了limit=2时，此时只会返回前2个数据
t_list = bs.find_all("a",limit=2)find_all除了上面一些常规的写法，还可以对其进行一些简写：
# 下面两者是相等的
t_list = bs.find_all("a")
t_list = bs("a")
# 下面两者是相等的
t_list = bs.a.find_all(text="新闻")
t_list = bs.a(text="新闻")2、find()
find()将返回符合条件的第一个Tag，有时我们只需要或一个Tag时，我们就可以用到find()方法了。当然了，也可以使用find_all()方法，传入一个limit=1，然后再取出第一个值也是可以的，不过未免繁琐。
t_list = bs.find_all("title",limit=1) # 返回只有一个结果的列表
t = bs.find("title") # 返回唯一值
t = bs.find("abc") # 如果没有找到，则返回None从结果可以看出find_all，尽管传入了limit=1，但是返回值仍然为一个列表，当我们只需要取一个值时，远不如find方法方便。但是如果未搜索到值时，将返回一个None。
在上面介绍BeautifulSoup4的时候，我们知道可以通过bs.div来获取第一个div标签，如果我们需要获取第一个div下的第一个div，我们可以这样：
t = bs.div.div
# 等价于
t = bs.find("div").find("div")六、CSS选择器：select()方法
BeautifulSoup支持部分的CSS选择器，在Tag获取BeautifulSoup对象的.select()方法中传入字符串参数，即可使用CSS选择器的语法找到Tag:
print(bs.select('title')) # 1、通过标签名查找
print(bs.select('a'))
print(bs.select('.mnav')) # 2、通过类名查找
print(bs.select('#u1')) # 3、通过id查找
print(bs.select('div .bri')) # 4、组合查找
print(bs.select('a[class="bri"]')) # 5、属性查找
print(bs.select('a[href="http://tieba.baidu.com" rel="external nofollow" rel="external nofollow" ]'))
print(bs.select("head > title")) # 6、直接子标签查找
print(bs.select(".mnav ~ .bri")) # 7、兄弟节点标签查找
print(bs.select('title')[0].get_text()) # 8、获取内容七、综合实例：
from bs4 import BeautifulSoup
import requests,re
req_obj = requests.get('https://www.baidu.com')
soup = BeautifulSoup(req_obj.text,'lxml')
'''标签查找'''
print(soup.title) #只是查找出第一个
print(soup.find('title')) #效果和上面一样
print(soup.find_all('div')) #查出所有的div标签
'''获取标签里的属性'''
tag = soup.div
print(tag['class']) #多属性的话，会返回一个列表
print(tag['id']) #查找标签的id属性
print(tag.attrs) #查找标签所有的属性，返回一个字典（属性名：属性值）
'''标签包的字符串'''
tag = soup.title
print(tag.string) #获取标签里的字符串
tag.string.replace_with("哈哈") #字符串不能直接编辑，可以替换
'''子节点的操作'''
tag = soup.head
print(tag.title) #获取head标签后再获取它包含的子标签
'''contents 和 .children'''
tag = soup.body
print(tag.contents) #将标签的子节点以列表返回
print([child for child in tag.children]) #输出和上面一样
'''descendants'''
tag = soup.body
[print(child_tag) for child_tag in tag.descendants] #获取所有子节点和子子节点
'''strings和.stripped_strings'''
tag = soup.body
[print(str) for str in tag.strings] #输出所有所有文本内容
[print(str) for str in tag.stripped_strings] #输出所有所有文本内容，去除空格或空行
'''.parent和.parents'''
tag = soup.title
print(tag.parent) #输出便签的父标签
[print(parent) for parent in tag.parents] #输出所有的父标签
'''.next_siblings 和 .previous_siblings
查出所有的兄弟节点
'''
'''.next_element 和 .previous_element
下一个兄弟节点
'''
'''find_all的keyword 参数'''
soup.find_all(id='link2') #查找所有包含 id 属性的标签
soup.find_all(href=re.compile("elsie")) #href 参数,Beautiful Soup会搜索每个标签的href属性:
soup.find_all(id=True) #找出所有的有id属性的标签
soup.find_all(href=re.compile("elsie"), id='link1') #也可以组合查找
soup.find_all(attrs={"属性名": "属性值"}) #也可以通过字典的方式查找八、BeautifulSoup 和lxml（Xpath）对比
# test.py
# -*- coding: utf-8 -*-
import requests
from bs4 import BeautifulSoup, SoupStrainer
import traceback
import json
from lxml import etree
import re
import time
def getHtmlText(url):
try:
r = requests.get(url, headers=headers)
r.raise_for_status()
if r.encoding == 'ISO-8859-1':
r.encoding = r.apparent_encoding
return r.text
except:
traceback.print_exc()
# ----------使用BeautifulSoup解析------------------------
def parseWithBeautifulSoup(html_text):
soup = BeautifulSoup(html_text, 'lxml')
content = []
for mulu in soup.find_all(class_='mulu'): # 先找到所有的 div class=mulu 标记
# 找到div_h3 标记
h3 = mulu.find('h3')
if h3 != None:
h3_title = h3.string # 获取标题
lst = []
for a in mulu.select('div.box a'):
href = a.get('href') # 找到 href 属性
box_title = a.get('title') # 找到 title 属性
pattern = re.compile(r'\s*\[(.*)\]\s+(.*)') # (re) 匹配括号内的表达式，也表示一个组
match = pattern.search(box_title)
if match != None:
date = match.group(1)
real_title = match.group(2)
lst.append({'href':href,'title':real_title,'date':date})
content.append({'title':h3_title,'content':lst})
with open('dmbj_bs.json', 'w') as fp:
json.dump(content, fp=fp, indent=4)
# ----------使用Xpath解析------------------------
def parseWithXpath(html_text):
html = etree.HTML(html_text)
content = []
for div_mulu in html.xpath('.//*[@class="mulu"]')： # 先找到所有的 div class=mulu 标记
# 找到所有的 div_h3 标记
div_h3 = div_mulu.xpath('./div[@class="mulu-title"]/center/h3/text()')
if len(div_h3) > 0:
h3_title = div_h3[0] # 获取标题
a_s = div_mulu.xpath('./div[@class="box"]/ul/li/a')
lst = []
for a in a_s:
href = a.xpath('./@href')[0] # 找到 href 属性
box_title = a.xpath('./@title')[0] # 找到 title 属性
pattern = re.compile(r'\s*\[(.*)\]\s+(.*)') # (re) 匹配括号内的表达式，也表示一个组
match = pattern.search(box_title)
if match != None:
date = match.group(1)
real_title = match.group(2)
lst.append({'href':href,'title':real_title,'date':date})
content.append({'title':h3_title,'content':lst})
with open('dmbj_xp.json', 'w') as fp:
json.dump(content, fp=fp, indent=4)
def main():
html_text = getHtmlText('http://www.seputu.com')
print(len(html_text))
start = time.clock()
parseWithBeautifulSoup(html_text)
print('BSoup cost:', time.clock()-start)
start = time.clock()
parseWithXpath(html_text)
print('Xpath cost:', time.clock()-start)
if __name__ == '__main__':
user_agent = 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.117 Safari/537.36'
headers={'User-Agent': user_agent}
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