bs4
from bs4 import BeautifulSoup
读取本地文件
soup = BeautifulSoup(open('baike.html', encoding='utf8'), "html.parser")
get_text()
如果只想得到tag中包含的文本内容,那么可以调用 get_text() 方法,这个方法获取到tag中包含的所有文版内容包括子孙tag中的内容,并将结果作为Unicode字符串返回:
tag
点取属性的方式只能获得当前名字的第一个tag
tag_a = soup.a
如果想要得到所有的<a>标签,或是通过名字得到比一个tag更多的内容的时候,就需要用到 Searching the tree 中描述的方法,比如: find_all()
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>]
tag中最重要的属性: name和attributes
tag.name是标签名
soup = BeautifulSoup('<b class="boldest">Extremely bold</b>')
tag = soup.b
type(tag)
# <class 'bs4.element.Tag'>
tag['class']
# u'boldest'
tag.get('class')
多值属性
一个tag可以有多个CSS的class，在Beautiful Soup中多值属性的返回类型是list；
css_soup = BeautifulSoup('<p class="body strikeout"></p>')
css_soup.p['class']
# ["body", "strikeout"]
注意：
如果某个属性看起来好像有多个值,但在任何版本的HTML定义中都没有被定义为多值属性,那么Beautiful Soup会将这个属性作为字符串返回
id_soup = BeautifulSoup('<p id="my id"></p>')
id_soup.p['id']
# 'my id'
如果转换的文档是XML格式,那么tag中不包含多值属性
xml_soup = BeautifulSoup('<p class="body strikeout"></p>', 'xml')
xml_soup.p['class']
# u'body strikeout'
string
字符串常被包含在tag内.Beautiful Soup用 NavigableString 类来包装tag中的字符串:
tag.string
# u'Extremely bold'
type(tag.string)
# <class 'bs4.element.NavigableString'>
编码转换
通过 unicode() 方法可以直接将 NavigableString 对象转换成Unicode字符串:
unicode_string = unicode(tag.string)
unicode_string
# u'Extremely bold'
type(unicode_string)
# <type 'unicode'>
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.
.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_tag
# <head><title>The Dormouse's story</title></head>
head_tag.contents
[<title>The Dormouse's story</title>]
title_tag = head_tag.contents[0]
title_tag
# <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 title_tag.children:
print(child)
# The Dormouse's story
string
如果一个tag仅有一个子节点,那么这个tag也可以使用 .string 方法。如果tag包含了多个子节点,tag就无法确定 .string 方法应该调用哪个子节点的内容, .string 的输出结果是 None
What’s it meaning?
如果tag中包含多个字符串 [2] ,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'
输出的字符串中可能包含了很多空格或空行,使用 .stripped_strings 可以去除多余空白内容:
for string in soup.stripped_strings:
print(repr(string))
What’s the repr() ?
兄弟节点
.next_sibling 和 .previous_sibling
需要小心，上一个<a>标签和下一个<a>标签之间的顿号和换行符;
<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>
link = soup.a
link
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>
link.next_sibling
# u',\n'
link.next_sibling.next_sibling
# <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>
迭代获取兄弟节点
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'
.next_elements 和 .previous_elements
两个tag之间的字符串，也会被认为是elements。
解析器先进入<a>标签,然后是tag中间的字符串,然后关闭</a>标签
下面的代码，有助于理解next_siblings和next_elements的区别
from bs4 import BeautifulSoup
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')
tag_a = soup.a
ans = []
for b in tag_a.next_siblings:
print(type(b))
ans.append(b.get_text())
print(ans)
ans = []
for n_e in tag_a.next_elements:
# print(type(n_e))
print(n_e)
ans.append(n_e.get_text())
print(ans)