Beautiful Soup 4 修改文档

2021-05-21 15:26 更新

Beautiful Soup的强项是文档树的搜索,但同时也可以方便的修改文档树。

修改tag的名称和属性

在 Attributes 的章节中已经介绍过这个功能,但是再看一遍也无妨. 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/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >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/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >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()​ 方法想tag中添加内容,就好像Python的列表的 ​.append()​ 方法:

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']

NavigableString() 和 .new_tag()

如果想添加一段文本内容到文档中也没问题,可以调用Python的 ​append()​ 方法 或调用 ​NavigableString​ 的构造方法:

soup = BeautifulSoup("<b></b>")
tag = soup.b
tag.append("Hello")
new_string = NavigableString(" there")
tag.append(new_string)
tag
# <b>Hello there.</b>
tag.contents
# [u'Hello', u' there']

如果想要创建一段注释,或 ​NavigableString​ 的任何子类, 只要调用 NavigableString 的构造方法:

from bs4 import Comment
new_comment = soup.new_string("Nice to see you.", Comment)
tag.append(new_comment)
tag
# <b>Hello there<!--Nice to see you.--></b>
tag.contents
# [u'Hello', u' there', u'Nice to see you.']

# 这是Beautiful Soup 4.2.1 中新增的方法

创建一个tag最好的方法是调用工厂方法 ​BeautifulSoup.new_tag()​ :

soup = BeautifulSoup("<b></b>")
original_tag = soup.b

new_tag = soup.new_tag("a", href="http://www.example.com" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" )
original_tag.append(new_tag)
original_tag
# <b><a href="http://www.example.com" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" ></a></b>

new_tag.string = "Link text."
original_tag
# <b><a href="http://www.example.com" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >Link text.</a></b>

第一个参数作为tag的name,是必填,其它参数选填

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.与Python列表总的 ​.insert()​ 方法的用法下同:

markup = '<a href="http://example.com/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >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/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >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']

clear()

Tag.clear()​ 方法移除当前tag的内容:

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

tag.clear()
tag
# <a href="http://example.com/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" ></a>

extract()

PageElement.extract()​ 方法将当前tag移除文档树,并作为方法结果返回:

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

i_tag = soup.i.extract()

a_tag
# <a href="http://example.com/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >I linked to</a>

i_tag
# <i>example.com</i>

print(i_tag.parent)
None

这个方法实际上产生了2个文档树: 一个是用来解析原始文档的 ​BeautifulSoup​ 对象,另一个是被移除并且返回的tag.被移除并返回的tag可以继续调用 ​extract​ 方法:

my_string = i_tag.string.extract()
my_string
# u'example.com'

print(my_string.parent)
# None
i_tag
# <i></i>

decompose()

Tag.decompose()​ 方法将当前节点移除文档树并完全销毁:

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

soup.i.decompose()

a_tag
# <a href="http://example.com/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >I linked to</a>

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/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >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/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >I linked to <b>example.net</b></a>

replace_with()​ 方法返回被替代的tag或文本节点,可以用来浏览或添加到文档树其它地方

wrap()

PageElement.wrap()​ 方法可以对指定的tag元素进行包装 [8] ,并返回包装后的结果:

soup = BeautifulSoup("<p>I wish I was bold.</p>")
soup.p.string.wrap(soup.new_tag("b"))
# <b>I wish I was bold.</b>

soup.p.wrap(soup.new_tag("div"))
# <div><p><b>I wish I was bold.</b></p></div>

该方法在 Beautiful Soup 4.0.5 中添加

unwrap()

Tag.unwrap()​ 方法与 ​wrap()​ 方法相反.将移除tag内的所有tag标签,该方法常被用来进行标记的解包:

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

a_tag.i.unwrap()
a_tag
# <a href="http://example.com/" rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank"  rel="external nofollow" target="_blank" >I linked to example.com</a>

与 ​replace_with()​ 方法相同, ​unwrap()​ 方法返回被移除的tag

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