Beautiful Soup 4 修改文檔
2021-05-21 15:26 更新
Beautiful Soup的強(qiáng)項(xiàng)是文檔樹的搜索,但同時(shí)也可以方便的修改文檔樹。
修改tag的名稱和屬性
在 Attributes 的章節(jié)中已經(jīng)介紹過這個(gè)功能,但是再看一遍也無妨. 重命名一個(gè)tag,改變屬性的值,添加或刪除屬性:
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
給tag的 ?.string? 屬性賦值,就相當(dāng)于用當(dāng)前的內(nèi)容替代了原來的內(nèi)容:
markup = '<a rel="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 rel="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: 如果當(dāng)前的tag包含了其它tag,那么給它的 ?.string? 屬性賦值會(huì)覆蓋掉原有的所有內(nèi)容包括子tag
append()
?Tag.append()? 方法想tag中添加內(nèi)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內(nèi)容到文檔中也沒問題,可以調(diào)用Python的 ?append()? 方法 或調(diào)用 ?NavigableString? 的構(gòu)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?jiǎng)?chuàng)建一段注釋,或 ?NavigableString? 的任何子類, 只要調(diào)用 NavigableString 的構(gòu)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.']
# 這是Beautiful Soup 4.2.1 中新增的方法
創(chuàng)建一個(gè)tag最好的方法是調(diào)用工廠方法 ?BeautifulSoup.new_tag()? :
soup = BeautifulSoup("<b></b>")
original_tag = soup.b
new_tag = soup.new_tag("a", rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" )
original_tag.append(new_tag)
original_tag
# <b><a 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 rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" >Link text.</a></b>
第一個(gè)參數(shù)作為tag的name,是必填,其它參數(shù)選填
insert()
?Tag.insert()? 方法與 ?Tag.append()? 方法類似,區(qū)別是不會(huì)把新元素添加到父節(jié)點(diǎn) ?.contents? 屬性的最后,而是把元素插入到指定的位置.與Python列表總的 ?.insert()? 方法的用法下同:
markup = '<a rel="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 rel="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()? 方法在當(dāng)前tag或文本節(jié)點(diǎn)前插入內(nèi)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()? 方法在當(dāng)前tag或文本節(jié)點(diǎn)后插入內(nèi)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()? 方法移除當(dāng)前tag的內(nèi)容:
markup = '<a rel="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 rel="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()? 方法將當(dāng)前tag移除文檔樹,并作為方法結(jié)果返回:
markup = '<a rel="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 rel="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
這個(gè)方法實(shí)際上產(chǎn)生了2個(gè)文檔樹: 一個(gè)是用來解析原始文檔的 ?BeautifulSoup? 對(duì)象,另一個(gè)是被移除并且返回的tag.被移除并返回的tag可以繼續(xù)調(diào)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()? 方法將當(dāng)前節(jié)點(diǎn)移除文檔樹并完全銷毀:
markup = '<a rel="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 rel="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()? 方法移除文檔樹中的某段內(nèi)容,并用新tag或文本節(jié)點(diǎn)替代它:
markup = '<a rel="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 rel="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或文本節(jié)點(diǎn),可以用來瀏覽或添加到文檔樹其它地方
wrap()
?PageElement.wrap()? 方法可以對(duì)指定的tag元素進(jìn)行包裝 [8] ,并返回包裝后的結(jié)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>
該方法在 Beautiful Soup 4.0.5 中添加
unwrap()
?Tag.unwrap()? 方法與 ?wrap()? 方法相反.將移除tag內(nèi)的所有tag標(biāo)簽,該方法常被用來進(jìn)行標(biāo)記的解包:
markup = '<a rel="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 rel="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>
與 ?replace_with()? 方法相同, ?unwrap()? 方法返回被移除的tag
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