读BeautifulSoup官方文档之html树的修改

修改html树无非是对其中标签的改动, 改动标签的名字(也就是类型), 属性和标签里的内容... 先讲这边提供了很方便的方法来对其进行改动...

 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>

然后是改动内容 :

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>

当然你还可以用append(), 我让我奇怪的是使用append()之后的效果看上去是一样的, 但是调用.contents却会发现其实append()是在.contents代表的那个list中append. 另一方面, 你还可以用一个 NavigableString替代String, 也是一样的.

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']

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']

当然你还可以用append()在tag内部添加注释 :

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

你甚至可以直接创建一个新的tag, 对于new_tag(), 它只有第一个参数是必须的 :

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

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

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

除了append()还有insert(), 它的插入, 从原理上来看也是插入了.contents 返回的那个list.

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>]

有关insert还有insert_before()和insert_after(), 就是插在当前调用tag的前面和后面.

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>

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()很简单, 就是把所调用标签的内容全部清除.

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

tag.clear()
tag
# <a href="http://example.com/"></a>

比clear()更神奇的是另外一个extract(),  extract()能够讲所调用的tag从html树中抽出, 同时返回提取的tag, 此时原来html树的该tag被删除.

markup = '<a href="http://example.com/">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/">I linked to</a>

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

print(i_tag.parent)
None

decompose()和extract()的区别就在于它完全毁掉所调用标签, 而不返回(这里要注意remove()是毁掉所调用标签的内容...).

markup = '<a href="http://example.com/">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/">I linked to</a>

replace_with()能够将其调用标签调换成参数标签, 同时返回调用标签...(相当于比extract()多了一个insert()的步骤)

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>

还有wrap()和unwrap(), 好像是用参数标签包住调用标签, 而unwrap()则用调用标签的内容替代调用标签本身.

 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>

 markup = '<a href="http://example.com/">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/">I linked to example.com</a>