Python商业数据挖掘实战——爬取网页并将其转为Markdown

前言

「作者主页」：雪碧有白泡泡
「个人网站」：雪碧的个人网站

ChatGPT体验地址

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_pos
        self.end_pos = end_pos
        self.content = content
        self._elements = []
        self.is_block = is_block
        self.tag = tag
        self._result = None

        if 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._result

    def 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 = html
        self.options = options
        self._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 = True
                for e in elements:
                    if e.start_pos < m.start() and e.end_pos > m.end():
                        can_append = False
                    elif 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

    @property
    def 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:
			pass
		path = os.path.join(folder, file_name)
		file = open(path,"w")
		file.close()
	else:
		path = os.path.join(folder, file_name)
	return path


def 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 cookies


def 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:
			pass


class TaskQueue(object):
	def __init__(self):
		self.VisitedList = []
		self.UnVisitedList = []
	
	def getVisitedList(self):
		return self.VisitedList

	def getUnVisitedList(self):
		return self.UnVisitedList
	
	def 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 url
	
	def 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 = username
		self.TaskQueue = TaskQueue()
		self.folder_name = folder_name
		self.url_num = 1

	def start(self):
		num = 0
		articles = [None]
		while len(articles) > 0:
			num += 1
			url = u'https://blog.csdn.net/' + self.username + '/article/list/' + str(num)
			response = self.s.get(url=url, headers=self.headers)
			html = response.text
			soup = 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.text
		soup = 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markdown
		md = Tomd(str(content)).markdown
		return md


	def 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 += 1
		self.url_num = 1
	
	def 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 += 1
		except Exception:
			pass

	def 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_mem
    while 1:
        with lock:
            if total_mem > size:
                total_mem-= size
                break
        time.sleep(5)
    yield 
    with lock:
        total_mem += size


def 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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