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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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