Python爬虫入门BeautifulSoup模块
BeautifulSoup
BeautifulSoup是一个模块，该模块用于接收一个HTML或XML字符串，
然后将其进行格式化，之后遍可以使用他提供的方法进行快速查找指定元素，
从而使得在HTML或XML中查找指定元素变得简单。
安装：
pip install BeautifulSoup4
导入：
from bs4 import BeautifulSoup
beautifulsoup简单示例:
soup = BeautifulSoup(text, features="html.parser")
# 返回第一个对象
v1 = soup.find("div")
v1 = soup.find(id="i1")
v1 = soup.find("div", id="i1") # 组合使用
# 返回对象列表
v2 = soup.find_all("div")
v2 = soup.find_all(id="i1")
v2 = soup.find_all("div", id="i1") # 组合使用
tag.text # 获取文本
tag.attrs("href") # 获取属性代码示例
from bs4 import BeautifulSoup
html_doc = """
The Dormouse's story
asdf
The Dormouse's story总共
f
Once upon a time there were three little sisters; and their names were
Elsfie,
Lacie and
Tillie;
and they lived at the bottom of a well.
ad
sf
...
"""
soup = BeautifulSoup(html_doc, features="lxml")
# 找到第一个a标签
tag1 = soup.find(name='a')
# 找到所有的a标签
tag2 = soup.find_all(name='a')
# 找到id＝link2的标签
tag3 = soup.select('#link2')
1、 name，标签名称
tag = soup.find('a')
name = tag.name # 获取
print(name)
tag.name = 'span' # 设置
print(soup)2、 attrs，标签属性
tag = soup.find('a')
attrs = tag.attrs # 获取
print(attrs)
tag.attrs = {'ik':123} # 设置
tag.attrs['id'] = 'value' # 设置
print(soup)3、 children,所有子标签
body = soup.find('body')
v = body.children4、 descendants,所有子子孙孙标签
body = soup.find('body')
v = body.descendants5、 clear,将标签的所有子标签全部清空（保留标签名）
tag = soup.find('body')
tag.clear()
print(soup)6、decompose,递归的删除所有的标签
body = soup.find('body')
body.decompose()
print(soup)7、extract,递归的删除所有的标签，并获取删除的标签
body = soup.find('body')
v = body.extract()
print(soup)8、 decode,转换为字符串（含当前标签）；decode_contents（不含当前标签）
body = soup.find('body')
v = body.decode()
v = body.decode_contents()
print(v)9、encode,转换为字节（含当前标签）；encode_contents（不含当前标签）
body = soup.find('body')
v = body.encode()
v = body.encode_contents()
print(v)10、find,获取匹配的第一个标签
tag = soup.find('a')
print(tag)
tag = soup.find(name='a', attrs={'class': 'sister'},
recursive=True, text='Lacie')
tag = soup.find(name='a', class_='sister',
recursive=True, text='Lacie')
print(tag)11、find_all,获取匹配的所有标签
tags = soup.find_all('a')
print(tags)
tags = soup.find_all('a',limit=1)
print(tags)
tags = soup.find_all(name='a', attrs={'class': 'sister'},
recursive=True, text='Lacie')
tags = soup.find_all(name='a', class_='sister',
recursive=True, text='Lacie')
print(tags)
####### 列表 #######
v = soup.find_all(name=['a','div'])
print(v)
v = soup.find_all(class_=['sister0', 'sister'])
print(v)
v = soup.find_all(text=['Tillie'])
print(v, type(v[0]))
v = soup.find_all(id=['link1','link2'])
print(v)
v = soup.find_all(href=['link1','link2'])
print(v)
####### 正则 #######
import re
rep = re.compile('p')
rep = re.compile('^p') # 所有以p开头
v = soup.find_all(name=rep)
print(v)
rep = re.compile('sister.*')
v = soup.find_all(class_=rep)
print(v)
rep = re.compile('http://www.oldboy.com/static/.*')
v = soup.find_all(href=rep)
print(v)
####### 方法筛选 #######
def func(tag):
return tag.has_attr('class') and tag.has_attr('id')
v = soup.find_all(name=func)
print(v)
## get,获取标签属性
tag = soup.find('a')
v = tag.get('id')
print(v)
12、has_attr,检查标签是否具有该属性
tag = soup.find('a')
v = tag.has_attr('id')
print(v)13、get_text,获取标签内部文本内容
tag = soup.find('a')
v = tag.get_text()
print(v)14、index,检查标签在某标签中的索引位置
tag = soup.find('body')
v = tag.index(tag.find('div'))
print(v)
tag = soup.find('body')
for i, v in enumerate(tag):
print(i,v)15、 is_empty_element,是否是空标签(是否可以是空)或者自闭合标签，
# 判断是否是如下标签：
# 'br' , 'hr', 'input', 'img', 'meta','spacer', 'link', 'frame', 'base'
tag = soup.find('br')
v = tag.is_empty_element
print(v)16、 当前的关联标签
tag.next
tag.next_element
tag.next_elements
tag.next_sibling
tag.next_siblings
tag.previous
tag.previous_element
tag.previous_elements
tag.previous_sibling
tag.previous_siblings
tag.parent
tag.parents
tag.children
tag.descendants17、查找某标签的关联标签
tag.find_next(...)
tag.find_all_next(...)
tag.find_next_sibling(...)
tag.find_next_siblings(...)
tag.find_previous(...)
tag.find_all_previous(...)
tag.find_previous_sibling(...)
tag.find_previous_siblings(...)
tag.find_parent(...)
tag.find_parents(...)
# 参数同find_all18、 select,select_one, CSS选择器
soup.select("title")
soup.select("p nth-of-type(3)")
soup.select("body a")
soup.select("html head title")
tag = soup.select("span,a")
soup.select("head > title")
soup.select("p > a")
soup.select("p > a:nth-of-type(2)")
soup.select("p > #link1")
soup.select("body > a")
soup.select("#link1 ~ .sister")
soup.select("#link1 + .sister")
soup.select(".sister")
soup.select("[class~=sister]")
soup.select("#link1")
soup.select("a#link2")
soup.select('a[href]')
soup.select('a[href="http://example.com/elsie"]')
soup.select('a[href^="http://example.com/"]')
soup.select('a[href$="tillie"]')
soup.select('a[href*=".com/el"]')
from bs4.element import Tag
def default_candidate_generator(tag):
for child in tag.descendants:
if not isinstance(child, Tag):
continue
if not child.has_attr('href'):
continue
yield child
tags = soup.find('body').select("a", _candidate_generator=default_candidate_generator)
print(type(tags), tags)
from bs4.element import Tag
def default_candidate_generator(tag):
for child in tag.descendants:
if not isinstance(child, Tag):
continue
if not child.has_attr('href'):
continue
yield child
tags = soup.find('body').select("a", _candidate_generator=default_candidate_generator, limit=1)
print(type(tags), tags)19、 标签的内容
tag = soup.find('span')
print(tag.string) # 获取
tag.string = 'new content' # 设置
print(soup)
tag = soup.find('body')
print(tag.string)
tag.string = 'xxx'
print(soup)
tag = soup.find('body')
v = tag.stripped_strings # 递归内部获取所有标签的文本
print(v)20、append在当前标签内部追加一个标签
tag = soup.find('body')
tag.append(soup.find('a'))
print(soup)
from bs4.element import Tag
obj = Tag(name='i',attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('body')
tag.append(obj)
print(soup)21、insert在当前标签内部指定位置插入一个标签
from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('body')
tag.insert(2, obj)
print(soup)22、 insert_after,insert_before 在当前标签后面或前面插入
from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('body')
tag.insert_before(obj)
tag.insert_after(obj)
print(soup)23、 replace_with 在当前标签替换为指定标签
from bs4.element import Tag
obj = Tag(name='i', attrs={'id': 'it'})
obj.string = '我是一个新来的'
tag = soup.find('div')
tag.replace_with(obj)
print(soup)24、 创建标签之间的关系
tag = soup.find('div')
a = soup.find('a')
tag.setup(previous_sibling=a)
print(tag.previous_sibling)25、wrap，将指定标签把当前标签包裹起来
from bs4.element import Tag
obj1 = Tag(name='div', attrs={'id': 'it'})
obj1.string = '我是一个新来的'
tag = soup.find('a')
v = tag.wrap(obj1)
print(soup)
tag = soup.find('a')
v = tag.wrap(soup.find('p'))
print(soup)
26、 unwrap，去掉当前标签，将保留其包裹的标签
tag = soup.find('a')
v = tag.unwrap()
print(soup)参考：
武沛齐：http://www.cnblogs.com/wupeiqi/articles/6283017.html
官方文档：http://beautifulsoup.readthedocs.io/zh_CN/v4.4.0/