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  • [Python] Wikipedia Crawler

    import time
    import urllib
    
    import bs4
    import requests
    
    
    start_url = "https://en.wikipedia.org/wiki/Special:Random"
    target_url = "https://en.wikipedia.org/wiki/Philosophy"
    
    def find_first_link(url):
        response = requests.get(url)
        html = response.text
        soup = bs4.BeautifulSoup(html, "html.parser")
    
        # This div contains the article's body
        # (June 2017 Note: Body nested in two div tags)
        content_div = soup.find(id="mw-content-text").find(class_="mw-parser-output")
    
        # stores the first link found in the article, if the article contains no
        # links this value will remain None
        article_link = None
    
        # Find all the direct children of content_div that are paragraphs
        for element in content_div.find_all("p", recursive=False):
            # Find the first anchor tag that's a direct child of a paragraph.
            # It's important to only look at direct children, because other types
            # of link, e.g. footnotes and pronunciation, could come before the
            # first link to an article. Those other link types aren't direct
            # children though, they're in divs of various classes.
            if element.find("a", recursive=False):
                article_link = element.find("a", recursive=False).get('href')
                break
    
        if not article_link:
            return
    
        # Build a full url from the relative article_link url
        first_link = urllib.parse.urljoin('https://en.wikipedia.org/', article_link)
    
        return first_link
    
    def continue_crawl(search_history, target_url, max_steps=25):
        if search_history[-1] == target_url:
            print("We've found the target article!")
            return False
        elif len(search_history) > max_steps:
            print("The search has gone on suspiciously long, aborting search!")
            return False
        elif search_history[-1] in search_history[:-1]:
            print("We've arrived at an article we've already seen, aborting search!")
            return False
        else:
            return True
    
    article_chain = [start_url]
    
    while continue_crawl(article_chain, target_url):
        print(article_chain[-1])
    
        first_link = find_first_link(article_chain[-1])
        if not first_link:
            print("We've arrived at an article with no links, aborting search!")
            break
    
        article_chain.append(first_link)
    
        time.sleep(2) # Slow things down so as to not hammer Wikipedia's servers
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  • 原文地址:https://www.cnblogs.com/Answer1215/p/7999777.html
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