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
content_div = soup.find(id="mw-content-text")
# 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