在Python的网络爬虫中，BeautifulSoup库是一个重要的网页解析工具。在初级教程中，咱们曾经理解了BeautifulSoup库的根本应用办法。在本篇文章中，咱们将深刻学习BeautifulSoup库的进阶应用。
一、简单的查找条件
在应用find和find_all办法查找元素时，咱们能够应用简单的查找条件，例如咱们能够查找所有class为"story"的p标签：
from bs4 import BeautifulSouphtml_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</p>"""soup = BeautifulSoup(html_doc, 'html.parser')story_p_tags = soup.find_all('p', class_='story')for p in story_p_tags: print(p.string)二、遍历DOM树
在BeautifulSoup中，咱们能够不便的遍历DOM树，以下是一些罕用的遍历办法：
from bs4 import BeautifulSouphtml_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</p>"""soup = BeautifulSoup(html_doc, 'html.parser')# 获取间接子节点for child in soup.body.children: print(child)# 获取所有子孙节点for descendant in soup.body.descendants: print(descendant)# 获取兄弟节点for sibling in soup.p.next_siblings: print(sibling)# 获取父节点print(soup.p.parent)三、批改DOM树
除了遍历DOM树，咱们还能够批改DOM树，例如咱们能够批改tag的内容和属性：
from bs4 import BeautifulSouphtml_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</p>"""soup = BeautifulSoup(html_doc, 'html.parser')soup.p.string = 'New story'soup.p['class'] = 'new_title'print(soup.p)四、解析XML
除了解析HTML外，BeautifulSoup还能够解析XML，咱们只须要在创立BeautifulSoup对象时指定解析器为"lxml-xml"即可：
from bs4 import BeautifulSoupxml_doc = """<bookstore><book category="COOKING"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year></book></bookstore>"""soup = BeautifulSoup(xml_doc, 'lxml-xml')print(soup.prettify())以上就是BeautifulSoup库的进阶应用办法，通过本篇文章，咱们能够更好地应用BeautifulSoup库进行网页解析，以便更无效地进行网络爬虫。