bs4 - HTML操作 - IPS99技术分享

标签：story string bs4 tag 节点 soup HTML 操作 find

html_doc = """
<html><head><title>The Dormouse's story</title></head>
    <body>
<p class="title"><b>The Dormouse's story</b></p>

<p class="story">Once upon a time there were three little sisters; and their names were
<a href="http://example.com/elsie" class="sister" id="link1">Elsie</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.</p>

<p class="story">...</p>
"""

soup = BeautifulSoup(html_doc, 'html.parser')

遍历文档树

子节点

一个Tag可能包含多个字符串或其它的Tag,这些都是这个Tag的子节点。Beautiful Soup提供了许多操作和遍历子节点的属性

注意: Beautiful Soup中字符串节点不支持这些属性,因为字符串没有子节点

tag的名字

head_tag = soup.head
# <head><title>The Dormouse's story</title></head>
head_name = head_tag.name
# head

.contents 和 .children

tag的.contents属性可以将tag的子节点以列表的方式输出

head_tag = soup.head
# <head><title>The Dormouse's story</title></head>

head_tag.contents
# [<title>The Dormouse's story</title>]

title_tag = head_tag.contents[0]
# <title>The Dormouse's story</title>
title_tag.contents
# [u'The Dormouse's story']

通过tag的 .children 生成器,可以对tag的子节点进行循环

for child in soup.title.children:
    print(child)
    # The Dormouse's story

.descendants

.descendants 属性可以对所有tag的子孙节点进行递归循环

for child in head_tag.descendants:
    print(child)
    # <title>The Dormouse's story</title>
    # The Dormouse's story

BeautifulSoup 有一个直接子节点(<html>节点)，却有很多子孙节点

len(list(soup.children))
# 1
len(list(soup.descendants))
# 25

.string

tag如果仅有一个子节点或只有一个 NavigableString 类型子节点，都可以用.string获取子节点（文本）

# 只有一个NavigableString类型子节点
soup.title.string
# u'The Dormouse's story'


# 仅有一个子节点
soup.head.contents
# [<title>The Dormouse's story</title>]
soup.head.string
# u'The Dormouse's story'

.strings 和 .stripped_strings

如果tag中包含多个字符串 ,可以使用 .strings 来循环获取

for string in soup.strings:
    print(repr(string))
    # u"The Dormouse's story"
    # u'\n\n'
    # u"The Dormouse's story"
    # u'\n\n'
    # u'Once upon a time there were three little sisters; and their names were\n'
    # u'Elsie'
    # u',\n'
    # u'Lacie'
    # u' and\n'
    # u'Tillie'
    # u';\nand they lived at the bottom of a well.'
    # u'\n\n'
    # u'...'
    # u'\n'

使用 .stripped_strings 可以去除多余空白内容

for string in soup.stripped_strings:
    print(repr(string))
    # u"The Dormouse's story"
    # u"The Dormouse's story"
    # u'Once upon a time there were three little sisters; and their names were'
    # u'Elsie'
    # u','
    # u'Lacie'
    # u'and'
    # u'Tillie'
    # u';\nand they lived at the bottom of a well.'
    # u'...'

父节点

.parent 和 .parents

通过 .parent 属性来获取某个元素的父节点

title_tag = soup.title
# <title>The Dormouse's story</title>
title_tag.parent
# <head><title>The Dormouse's story</title></head>

通过元素的 .parents 属性可以递归得到元素的所有父辈节点

link = soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>
for parent in link.parents:
    if parent is None:
        print(parent)
    else:
        print(parent.name)
# p
# body
# html
# [document]
# None

兄弟节点

.next_sibling 和 .previous_sibling

在文档树中,使用 .next_sibling 和 .previous_sibling 属性来查询兄弟节点

"""
<html>
  <body>
    <a>
      <b>text1</b>
      <c>text2</c>
    </a>
  </body>
</html>
"""

sibling_soup.b.next_sibling
# <c>text2</c>

sibling_soup.c.previous_sibling
# <b>text1</b>

.next_siblings 和 .previous_siblings

通过 .next_siblings 和 .previous_siblings 属性可以对当前节点的兄弟节点迭代输出

for sibling in soup.a.next_siblings:
    print(repr(sibling))
    # u',\n'
    # <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
    # u' and\n'
    # <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>
    # u'; and they lived at the bottom of a well.'
    # None

for sibling in soup.find(id="link3").previous_siblings:
    print(repr(sibling))
    # ' and\n'
    # <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
    # u',\n'
    # <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>
    # u'Once upon a time there were three little sisters; and their names were\n'
    # None

前进和回退

.next_element 和 .previous_element

.next_element 属性指向解析过程中下一个被解析的对象(字符串或tag),结果可能与 .next_sibling 相同,但通常是不一样的

last_a_tag = soup.find("a", id="link3")
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>

last_a_tag.next_sibling
# '; \nand they lived at the bottom of a well.'

这个<a>标签的 .next_element 属性结果是在<a>标签被解析之后的解析内容，不是<a>标签后的句子部分,应该是字符串Tillie。这是因为在原始文档中,字符串Tillie 在分号前出现，解析器先进入<a>标签，然后是字符串Tillie，然后关闭</a>标签,然后是分号和剩余部分。分号与<a>标签在同一层级,但是字符串Tillie会被先解析

last_a_tag.next_element
# u'Tillie'

.previous_element 属性刚好与 .next_element 相反,它指向当前被解析的对象的前一个解析对象

last_a_tag.previous_element
# u' and\n'
last_a_tag.previous_element.next_element
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>

.next_elements 和 .previous_elements

通过 .next_elements 和 .previous_elements 的迭代器就可以向前或向后访问文档的解析内容，就好像文档正在被解析一样

for element in last_a_tag.next_elements:
    print(repr(element))
# u'Tillie'
# u';\nand they lived at the bottom of a well.'
# u'\n\n'
# <p class="story">...</p>
# u'...'
# u'\n'
# None

搜索文档树

find() 和 find_all()

find/find_all( name , attrs , recursive , string , **kwargs )

使用方法相同，唯一区别，find返回值是元素本身，不存在时返回None；find_all返回值是n个元素的列表，不存在时返回空列表

搜索当前tag的所有子节点，并判断是否符合过滤器的条件

soup.find_all("title")
# [<title>The Dormouse's story</title>]

soup.find_all("p", "title")
# [<p class="title"><b>The Dormouse's story</b></p>]

soup.find_all("a")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.find_all(id="link2")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

import re
soup.find(string=re.compile("sisters"))
# u'Once upon a time there were three little sisters; and their names were\n'

keyword参数

1、如果一个参数不是函数的形参搜索时会把该参数当作指定名字tag的属性来搜索

soup.find_all(id='link2')
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

soup.find_all(href=re.compile("elsie"))
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

2、在文档树中查找所有包含 id 属性的tag,无论 id 的值是什么

soup.find_all(id=True)
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

3、使用多个指定名字的参数可以同时过滤tag的多个属性

soup.find_all(href=re.compile("elsie"), id='link1')
# [<a class="sister" href="http://example.com/elsie" id="link1">three</a>]

4、有些tag属性的搜索不能使用,比如HTML5中的 data-* 属性。但是可以通过 find_all() 方法的 attrs 参数定义一个字典参数来搜索包含特殊属性的tag

data_soup = BeautifulSoup('<div data-foo="value">foo!</div>')
data_soup.find_all(data-foo="value")
# SyntaxError: keyword can't be an expression

data_soup.find_all(attrs={"data-foo": "value"})
# [<div data-foo="value">foo!</div>]

按CSS搜索

Beautiful Soup的4.1.1版本开始,可以通过 class_ 参数搜索有指定CSS类名的tag

soup.find_all("a", class_="sister")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

1、class_ 参数同样接受不同类型的过滤器 ,字符串,正则表达式,方法或 True

soup.find_all(class_=re.compile("itl"))
# [<p class="title"><b>The Dormouse's story</b></p>]

def has_six_characters(css_class):
    return css_class is not None and len(css_class) == 6

soup.find_all(class_=has_six_characters)
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

2、tag的 class 属性是,按照CSS类名搜索tag时,可以分别搜索tag中的每个CSS类名,也可以通过CSS值完全匹配:

css_soup = BeautifulSoup('<p class="body strikeout"></p>', 'lxml')
css_soup.find_all("p", class_="strikeout")
# [<p class="body strikeout"></p>]

css_soup.find_all("p", class_="body")
# [<p class="body strikeout"></p>]

css_soup.find_all("p", class_="body strikeout")
# [<p class="body strikeout"></p>]

注意：完全匹配 class 的值时,如果CSS类名的顺序与实际不符,将搜索不到结果:

css_soup.find_all("p", class_="strikeout body")
# []

string参数

通过 string 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, string 参数接受：字符串 , 正则表达式 , 列表, True 。

soup.find_all(string="Elsie")
# [u'Elsie']

soup.find_all(string=["Tillie", "Elsie", "Lacie"])
# [u'Elsie', u'Lacie', u'Tillie']

soup.find_all(string=re.compile("Dormouse"))
[u"The Dormouse's story", u"The Dormouse's story"]

def is_the_only_string_within_a_tag(s):
    ""Return True if this string is the only child of its parent tag.""
    return (s == s.parent.string)

soup.find_all(string=is_the_only_string_within_a_tag)
# [u"The Dormouse's story", u"The Dormouse's story", u'Elsie', u'Lacie', u'Tillie', u'...']

还可以与其它参数混合使用来过滤tag.Beautiful Soup会找到 .string 方法与 string 参数值相符的tag

soup.find_all("a", string="Elsie")
# [<a href="http://example.com/elsie" class="sister" id="link1">Elsie</a>]

limit参数

限制返回结果的数量

soup.find_all("a", limit=2)
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

recursive参数

调用tag的 find_all() 方法时,Beautiful Soup会检索当前tag的所有子孙节点,如果只想搜索tag的直接子节点,可以使用参数 recursive=False .

soup.html.find_all("title")
# [<title>The Dormouse's story</title>]

soup.html.find_all("title", recursive=False)
# []

<title>标签在<html>标签下, 但并不是直接子节点, <head>标签才是直接子节点. 在允许查询所有后代节点时Beautiful Soup能够查找到<title>标签. 但是使用了 recursive=False 参数之后,只能查找直接子节点,这样就查不到<title>标签了

tag也可以被调用

BeautifulSoup 对象和 tag 对象可以被当作一个方法来使用,这个方法的执行结果与调用这个对象的 find_all() 方法相同,如下:

soup.find_all("a")
soup("a")

或者:

soup.title.find_all(string=True)
soup.title(string=True)

拓展：soup.head.title 是tag的名字方法的简写.这个简写的原理就是多次调用当前tag的 find() 方法

soup.head.title
# <title>The Dormouse's story</title>

soup.find("head").find("title")
# <title>The Dormouse's story</title>

find_parents() 和 find_parent()

find_parents( name , attrs , recursive , string , **kwargs )

a_string = soup.find(string="Lacie")
# u'Lacie'

a_string.find_parents("a")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

a_string.find_parent("p")
# <p class="story">Once upon a time there were three little sisters; and their names were
#  <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a> and
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>;
#  and they lived at the bottom of a well.</p>

a_string.find_parents("p", class="title")
# []

文档中的一个<a>标签是当前子节点的直接父节点,所以可以被找到.还有一个<p>标签是目标子节点的间接父辈节点,所以也可以被找到.包含class值为title的<p>标签不是目标子节点的父辈节点,所以通过 find_parents() 方法搜索不到.

find_next_siblings() 和 find_next_sibling()

find_next_siblings( name , attrs , recursive , string , **kwargs

find_next_siblings() 方法返回所有符合条件的后面的兄弟节点, find_next_sibling() 只返回符合条件的后面的第一个tag节点

first_link = soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>

first_link.find_next_siblings("a")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

first_story_paragraph = soup.find("p", "story")
first_story_paragraph.find_next_sibling("p")
# <p class="story">...</p>

find_previous_siblings() 和 find_previous_sibling()

find_previous_siblings( name , attrs , recursive , string , **kwargs )

find_previous_siblings() 方法返回所有符合条件的前面的兄弟节点, find_previous_sibling() 方法返回第一个符合条件的前面的兄弟节点

last_link = soup.find("a", id="link3")
# <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>

last_link.find_previous_siblings("a")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

first_story_paragraph = soup.find("p", "story")
first_story_paragraph.find_previous_sibling("p")
# <p class="title"><b>The Dormouse's story</b></p>

find_all_next() 和 find_next()

find_all_next( name , attrs , recursive , string , **kwargs )

这2个方法通过.next_elements属性对当前tag之后的tag和字符串进行迭代, find_all_next() 方法返回所有符合条件的节点, find_next() 方法返回第一个符合条件的节点

first_link = soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>

first_link.find_all_next(string=True)
# [u'Elsie', u',\n', u'Lacie', u' and\n', u'Tillie',
#  u';\nand they lived at the bottom of a well.', u'\n\n', u'...', u'\n']

first_link.find_next("p")
# <p class="story">...</p>

find_all_previous() 和 find_previous()

find_all_previous( name , attrs , recursive , string , **kwargs )

这2个方法通过.previous_elements属性对当前节点前面的tag和字符串进行迭代, find_all_previous() 方法返回所有符合条件的节点, find_previous() 方法返回第一个符合条件的节点

first_link = soup.a
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>

first_link.find_all_previous("p")
# [<p class="story">Once upon a time there were three little sisters; ...</p>,
#  <p class="title"><b>The Dormouse's story</b></p>]

first_link.find_previous("title")
# <title>The Dormouse's story</title>

CSS选择器

Beautiful Soup支持大部分的CSS选择器 http://www.w3.org/TR/CSS2/selector.html , 在 Tag 或 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

soup.select("title")
# [<title>The Dormouse's story</title>]

soup.select("p:nth-of-type(3)")
# [<p class="story">...</p>]

1、通过tag标签逐层查找

soup.select("body a")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie"  id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.select("html head title")
# [<title>The Dormouse's story</title>]

2、找到某个tag标签下的直接子标签

soup.select("head > title")
# [<title>The Dormouse's story</title>]

soup.select("p > a")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie"  id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.select("p > a:nth-of-type(2)")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

soup.select("p > #link1")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

soup.select("body > a")
# []

3、找到兄弟节点标签

soup.select("#link1 ~ .sister")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie"  id="link3">Tillie</a>]

soup.select("#link1 + .sister")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

4、通过CSS的类名查找

soup.select(".sister")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.select("[class~=sister]")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

5、通过tag的id查找

soup.select("#link1")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

soup.select("a#link2")
# [<a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

6、同时用多种CSS选择器查询元素

soup.select("#link1,#link2")
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>]

7、通过是否存在某个属性来查找

soup.select('a[href]')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

8、通过属性的值来查找

soup.select('a[href="http://example.com/elsie"]')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

soup.select('a[href^="http://example.com/"]')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>,
#  <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>,
#  <a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.select('a[href$="tillie"]')
# [<a class="sister" href="http://example.com/tillie" id="link3">Tillie</a>]

soup.select('a[href*=".com/el"]')
# [<a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>]

9、通过语言设置来查找

multilingual_markup = """
 <p lang="en">Hello</p>
 <p lang="en-us">Howdy, y'all</p>
 <p lang="en-gb">Pip-pip, old fruit</p>
 <p lang="fr">Bonjour mes amis</p>
"""
multilingual_soup = BeautifulSoup(multilingual_markup)
multilingual_soup.select('p[lang|=en]')
# [<p lang="en">Hello</p>,
#  <p lang="en-us">Howdy, y'all</p>,
#  <p lang="en-gb">Pip-pip, old fruit</p>]

10、返回查找到的元素的第一个

soup.select_one(".sister")
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>

修改文档树

修改tag的名称和属性

重命名一个tag,改变属性的值,添加或删除属性

soup = BeautifulSoup('<b class="boldest">Extremely bold</b>')
tag = soup.b

tag.name = "blockquote"
tag['class'] = 'verybold'
tag['id'] = 1
tag
# <blockquote class="verybold" id="1">Extremely bold</blockquote>

del tag['class']
del tag['id']
tag
# <blockquote>Extremely bold</blockquote>

修改 .string

给tag的 .string 属性赋值,就相当于用当前的内容替代了原来的内容

markup = '<a href="http://example.com/">I linked to <i>example.com</i></a>'
soup = BeautifulSoup(markup)

tag = soup.a
tag.string = "New link text."
tag
# <a href="http://example.com/">New link text.</a>

注意: 如果当前的tag包含了其它tag,那么给它的 .string 属性赋值会覆盖掉原有的所有内容包括子tag

append()

Tag.append() 方法向tag中添加内容

soup = BeautifulSoup("<a>Foo</a>")
soup.a.append("Bar")

soup
# <html><head></head><body><a>FooBar</a></body></html>
soup.a.contents
# [u'Foo', u'Bar']

insert()

Tag.insert() 方法与 Tag.append() 方法类似,区别是不会把新元素添加到父节点 .contents 属性的最后,而是把元素插入到指定的位置

markup = '<a href="http://example.com/">I linked to <i>example.com</i></a>'
soup = BeautifulSoup(markup)
tag = soup.a

tag.insert(1, "but did not endorse ")
tag
# <a href="http://example.com/">I linked to but did not endorse <i>example.com</i></a>
tag.contents
# [u'I linked to ', u'but did not endorse', <i>example.com</i>]

insert_before() 和 insert_after()

insert_before() 方法在当前tag或文本节点前插入内容

soup = BeautifulSoup("<b>stop</b>")
tag = soup.new_tag("i")
tag.string = "Don't"
soup.b.string.insert_before(tag)
soup.b
# <b><i>Don't</i>stop</b>

insert_after() 方法在当前tag或文本节点后插入内容

soup.b.i.insert_after(soup.new_string(" ever "))
soup.b
# <b><i>Don't</i> ever stop</b>
soup.b.contents
# [<i>Don't</i>, u' ever ', u'stop']

replace_with()

PageElement.replace_with() 方法移除文档树中的某段内容,并用新tag或文本节点替代它

markup = '<a href="http://example.com/">I linked to <i>example.com</i></a>'
soup = BeautifulSoup(markup)
a_tag = soup.a

new_tag = soup.new_tag("b")
new_tag.string = "example.net"
a_tag.i.replace_with(new_tag)

a_tag
# <a href="http://example.com/">I linked to <b>example.net</b></a>

标签：story,string,bs4,tag,节点,soup,HTML,操作,find
From： https://www.cnblogs.com/rong-z/p/17879908.html

bs4 - HTML操作