Python商业数据挖掘实战——爬取网页并将其转为Markdown

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「作者主页」：雪碧有白泡泡
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前言

在信息爆炸的时代，互联网上的海量文字信息如同无尽的沙滩。然而，其中真正有价值的信息往往埋在各种网页中，需要经过筛选和整理才能被有效利用。幸运的是，Python这个强大的编程语言可以帮助我们完成这项任务。

本文将介绍如何使用Python将网页文字转换为Markdown格式，这将使得我们能够更加方便地阅读和处理网页内容。无论是将文章保存为本地文件还是转化为其他格式，Markdown都能够提供清晰简洁的排版和格式，让我们更加专注于内容本身。

正则表达式

我们将页面进行Maekdown的转换为了保证准确度，我们可以使用正则表达式去修改，如下

import re__all__ = ['Tomd', 'convert']MARKDOWN = {'h1': ('\n# ', '\n'),'h2': ('\n## ', '\n'),'h3': ('\n### ', '\n'),'h4': ('\n#### ', '\n'),'h5': ('\n##### ', '\n'),'h6': ('\n###### ', '\n'),'code': ('`', '`'),'ul': ('', ''),'ol': ('', ''),'li': ('- ', ''),'blockquote': ('\n> ', '\n'),'em': ('**', '**'),'strong': ('**', '**'),'block_code': ('\n```\n', '\n```\n'),'span': ('', ''),'p': ('\n', '\n'),'p_with_out_class': ('\n', '\n'),'inline_p': ('', ''),'inline_p_with_out_class': ('', ''),'b': ('**', '**'),'i': ('*', '*'),'del': ('~~', '~~'),'hr': ('\n---', '\n\n'),'thead': ('\n', '|------\n'),'tbody': ('\n', '\n'),'td': ('|', ''),'th': ('|', ''),'tr': ('', '\n')
}BlOCK_ELEMENTS = {'h1': '<h1.*?>(.*?)</h1>','h2': '<h2.*?>(.*?)</h2>','h3': '<h3.*?>(.*?)</h3>','h4': '<h4.*?>(.*?)</h4>','h5': '<h5.*?>(.*?)</h5>','h6': '<h6.*?>(.*?)</h6>','hr': '<hr/>','blockquote': '<blockquote.*?>(.*?)</blockquote>','ul': '<ul.*?>(.*?)</ul>','ol': '<ol.*?>(.*?)</ol>','block_code': '<pre.*?><code.*?>(.*?)</code></pre>','p': '<p\s.*?>(.*?)</p>','p_with_out_class': '<p>(.*?)</p>','thead': '<thead.*?>(.*?)</thead>','tr': '<tr>(.*?)</tr>'
}INLINE_ELEMENTS = {'td': '<td>(.*?)</td>','tr': '<tr>(.*?)</tr>','th': '<th>(.*?)</th>','b': '<b>(.*?)</b>','i': '<i>(.*?)</i>','del': '<del>(.*?)</del>','inline_p': '<p\s.*?>(.*?)</p>','inline_p_with_out_class': '<p>(.*?)</p>','code': '<code.*?>(.*?)</code>','span': '<span.*?>(.*?)</span>','ul': '<ul.*?>(.*?)</ul>','ol': '<ol.*?>(.*?)</ol>','li': '<li.*?>(.*?)</li>','img': '<img.*?src="(.*?)".*?>(.*?)</img>','a': '<a.*?href="(.*?)".*?>(.*?)</a>','em': '<em.*?>(.*?)</em>','strong': '<strong.*?>(.*?)</strong>'
}DELETE_ELEMENTS = ['<span.*?>', '</span>', '<div.*?>', '</div>']class Element:def __init__(self, start_pos, end_pos, content, tag, is_block=False):self.start_pos = start_posself.end_pos = end_posself.content = contentself._elements = []self.is_block = is_blockself.tag = tagself._result = Noneif self.is_block:self.parse_inline()def __str__(self):wrapper = MARKDOWN.get(self.tag)self._result = '{}{}{}'.format(wrapper[0], self.content, wrapper[1])return self._resultdef parse_inline(self):for tag, pattern in INLINE_ELEMENTS.items():if tag == 'a':self.content = re.sub(pattern, '[\g<2>](\g<1>)', self.content)elif tag == 'img':self.content = re.sub(pattern, '![\g<2>](\g<1>)', self.content)elif self.tag == 'ul' and tag == 'li':self.content = re.sub(pattern, '- \g<1>', self.content)elif self.tag == 'ol' and tag == 'li':self.content = re.sub(pattern, '1. \g<1>', self.content)elif self.tag == 'thead' and tag == 'tr':self.content = re.sub(pattern, '\g<1>\n', self.content.replace('\n', ''))elif self.tag == 'tr' and tag == 'th':self.content = re.sub(pattern, '|\g<1>', self.content.replace('\n', ''))elif self.tag == 'tr' and tag == 'td':self.content = re.sub(pattern, '|\g<1>', self.content.replace('\n', ''))else:wrapper = MARKDOWN.get(tag)self.content = re.sub(pattern, '{}\g<1>{}'.format(wrapper[0], wrapper[1]), self.content)class Tomd:def __init__(self, html='', options=None):self.html = htmlself.options = optionsself._markdown = ''def convert(self, html, options=None):elements = []for tag, pattern in BlOCK_ELEMENTS.items():for m in re.finditer(pattern, html, re.I | re.S | re.M):element = Element(start_pos=m.start(),end_pos=m.end(),content=''.join(m.groups()),tag=tag,is_block=True)can_append = Truefor e in elements:if e.start_pos < m.start() and e.end_pos > m.end():can_append = Falseelif e.start_pos > m.start() and e.end_pos < m.end():elements.remove(e)if can_append:elements.append(element)elements.sort(key=lambda element: element.start_pos)self._markdown = ''.join([str(e) for e in elements])for index, element in enumerate(DELETE_ELEMENTS):self._markdown = re.sub(element, '', self._markdown)return self._markdown@propertydef markdown(self):self.convert(self.html, self.options)return self._markdown_inst = Tomd()
convert = _inst.convert

这段代码是一个用于将HTML转换为Markdown的工具类。它使用了正则表达式来解析HTML标签，并根据预定义的转换规则将其转换为对应的Markdown格式。

代码中定义了一个Element类，用于表示HTML中的各个元素。Element类包含了标签的起始位置、结束位置、内容、标签类型等信息。它还提供了一个parse_inline方法，用于解析内联元素，并将其转换为Markdown格式。

Tomd类是主要的转换类，它接受HTML字符串并提供了convert方法来执行转换操作。convert方法遍历预定义的HTML标签模式，并使用正则表达式匹配HTML字符串中对应的部分。然后创建相应的Element对象并进行转换操作。最后，将转换后的Markdown字符串返回。

在模块顶部，MARKDOWN字典定义了各个HTML标签对应的Markdown格式。BlOCK_ELEMENTS和INLINE_ELEMENTS字典定义了正则表达式模式，用于匹配HTML字符串中的块级元素和内联元素。DELETE_ELEMENTS列表定义了需要删除的HTML元素。

那么既然有了转markdown的工具，我们就可以对网页进行转换

进行转换

首先，result_file函数用于创建一个保存结果文件的路径。它接受文件夹的用户名、文件名和文件夹名作为参数，并在指定的文件夹路径下创建一个新的文件，并返回该文件的路径。

get_headers函数用于从一个文本文件中读取Cookie，并将它们保存为字典形式。它接受包含Cookie的文本文件路径作为参数。

delete_ele函数用于删除BeautifulSoup对象中指定的标签。它接受一个BeautifulSoup对象和待删除的标签列表作为参数，并通过使用该对象的select方法来选择要删除的标签，然后使用decompose方法进行删除。

delete_ele_attr函数用于删除BeautifulSoup对象中指定标签的指定属性。它接受一个BeautifulSoup对象和待删除的属性列表作为参数，并使用find_all方法来选取所有标签，然后使用Python的del语句删除指定的属性。

delete_blank_ele函数用于删除BeautifulSoup对象中的空白标签。它接受一个BeautifulSoup对象和一个例外列表，对于不在例外列表中且内容为空的标签，使用decompose方法进行删除。

TaskQueue类是一个简单的任务队列，用于存储已访问的和未访问的URL。它提供了一系列方法来操作这些列表。

def result_file(folder_username, file_name, folder_name):folder = os.path.join(os.path.dirname(os.path.realpath(__file__)), "..", folder_name, folder_username)if not os.path.exists(folder):try:os.makedirs(folder)except Exception:passpath = os.path.join(folder, file_name)file = open(path,"w")file.close()else:path = os.path.join(folder, file_name)return pathdef get_headers(cookie_path:str):cookies = {}with open(cookie_path, "r", encoding="utf-8") as f:cookie_list = f.readlines()for line in cookie_list:cookie = line.split(":")cookies[cookie[0]] = str(cookie[1]).strip()return cookiesdef delete_ele(soup:BeautifulSoup, tags:list):for ele in tags:for useless_tag in soup.select(ele):useless_tag.decompose()def delete_ele_attr(soup:BeautifulSoup, attrs:list):for attr in attrs:for useless_attr in soup.find_all():del useless_attr[attr]def delete_blank_ele(soup:BeautifulSoup, eles_except:list):for useless_attr in soup.find_all():try:if useless_attr.name not in eles_except and useless_attr.text == "":useless_attr.decompose()except Exception:passclass TaskQueue(object):def __init__(self):self.VisitedList = []self.UnVisitedList = []def getVisitedList(self):return self.VisitedListdef getUnVisitedList(self):return self.UnVisitedListdef InsertVisitedList(self, url):if url not in self.VisitedList:self.VisitedList.append(url)def InsertUnVisitedList(self, url):if url not in self.UnVisitedList:self.UnVisitedList.append(url)def RemoveVisitedList(self, url):self.VisitedList.remove(url)def PopUnVisitedList(self,index=0):url = []if index and self.UnVisitedList:url = self.UnVisitedList[index]del self.UnVisitedList[:index]elif self.UnVisitedList:url = self.UnVisitedList.pop()return urldef getUnVisitedListLength(self):return len(self.UnVisitedList)class CSDN(object):def __init__(self, username, folder_name, cookie_path):# self.headers = {# 	"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.70 Safari/537.36"# }self.headers = get_headers(cookie_path)self.s = requests.Session()self.username = usernameself.TaskQueue = TaskQueue()self.folder_name = folder_nameself.url_num = 1def start(self):num = 0articles = [None]while len(articles) > 0:num += 1url = u'https://blog.csdn.net/' + self.username + '/article/list/' + str(num)response = self.s.get(url=url, headers=self.headers)html = response.textsoup = BeautifulSoup(html, "html.parser")articles = soup.find_all('div', attrs={"class":"article-item-box csdn-tracking-statistics"})for article in articles:article_title = article.a.text.strip().replace('        ','：')article_href = article.a['href']with ensure_memory(sys.getsizeof(self.TaskQueue.UnVisitedList)):self.TaskQueue.InsertUnVisitedList([article_title, article_href])def get_md(self, url):response = self.s.get(url=url, headers=self.headers)html = response.textsoup = BeautifulSoup(html, 'lxml')content = soup.select_one("#content_views")# 删除注释for useless_tag in content(text=lambda text: isinstance(text, Comment)):useless_tag.extract()# 删除无用标签tags = ["svg", "ul", ".hljs-button.signin"]delete_ele(content, tags)# 删除标签属性attrs = ["class", "name", "id", "onclick", "style", "data-token", "rel"]delete_ele_attr(content,attrs)# 删除空白标签eles_except = ["img", "br", "hr"]delete_blank_ele(content, eles_except)# 转换为markdownmd = Tomd(str(content)).markdownreturn mddef write_readme(self):print("+"*100)print("[++] 开始爬取 {} 的博文 ......".format(self.username))print("+"*100)reademe_path = result_file(self.username,file_name="README.md",folder_name=self.folder_name)with open(reademe_path,'w', encoding='utf-8') as reademe_file:readme_head = "# " + self.username + " 的博文\n"reademe_file.write(readme_head)for [article_title,article_href] in self.TaskQueue.UnVisitedList[::-1]:text = str(self.url_num) + '. [' + article_title + ']('+ article_href +')\n'reademe_file.write(text)self.url_num += 1self.url_num = 1def get_all_articles(self):try:while True:[article_title,article_href] = self.TaskQueue.PopUnVisitedList()try:file_name = re.sub(r'[\/:：*?"<>|]','-', article_title) + ".md"artical_path = result_file(folder_username=self.username, file_name=file_name, folder_name=self.folder_name)md_head = "# " + article_title + "\n"md = md_head + self.get_md(article_href)print("[++++] 正在处理URL：{}".format(article_href))with open(artical_path, "w", encoding="utf-8") as artical_file:artical_file.write(md)except Exception:print("[----] 处理URL异常：{}".format(article_href))self.url_num += 1except Exception:passdef muti_spider(self, thread_num):while self.TaskQueue.getUnVisitedListLength() > 0:thread_list = []for i in range(thread_num):th = threading.Thread(target=self.get_all_articles)thread_list.append(th)for th in thread_list:th.start()lock = threading.Lock()
total_mem= 1024 * 1024 * 500 #500MB spare memory
@contextlib.contextmanager
def ensure_memory(size):global total_memwhile 1:with lock:if total_mem > size:total_mem-= sizebreaktime.sleep(5)yield with lock:total_mem += sizedef spider_user(username: str, cookie_path:str, thread_num: int = 10, folder_name: str = "articles"):if not os.path.exists(folder_name):os.makedirs(folder_name)csdn = CSDN(username, folder_name, cookie_path)csdn.start()th1 = threading.Thread(target=csdn.write_readme)th1.start()th2 = threading.Thread(target=csdn.muti_spider, args=(thread_num,))th2.start()def spider(usernames: list, cookie_path:str, thread_num: int = 10, folder_name: str = "articles"):for username in usernames:try:user_thread = threading.Thread(target=spider_user,args=(username, cookie_path, thread_num, folder_name))user_thread.start()print("[++] 开启爬取 {} 博文进程成功 ......".format(username))except Exception:print("[--] 开启爬取 {} 博文进程出现异常 ......".format(username))

我们可以自定义一个测试类运行一下，在本地文件位置会生成一个文件夹，并将markdown文件输出出来

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