wrapper.py

import requests
import time
import bs4
import urllib


def continue_crawl(search_history, target_url, max_steps=25):
    """
    function that checks if we achieve target article,
    get a loop or neither of them if searching takes
    too much steps
    """
    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


def find_first_link(url):
    """
    function that finds first link in the Wikipedia article
    """
    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 web_crawl():
    """
    final function which runs continue_crawl in a loop
    as long as it does not finds a target article, a loop
    or runs for too many times
    """
    while continue_crawl(article_chain, target_url):
        # download html of last article in article_chain
        response = article_chain[-1]
        # find the first link in that html
        first_link = find_first_link(response)
        # add the first link to article chain
        article_chain.append(first_link)
        # delay for about two seconds
        time.sleep(2)


# starting our wrapper
target_url = "https://en.wikipedia.org/wiki/Lewis_Hamilton"
article_chain = ["https://en.wikipedia.org/wiki/Robert_Kubica"]
web_crawl()