crawler.py

from urllib.request import urlopen
from urllib.parse import urlparse
from bs4 import BeautifulSoup
import re
import datetime
import random

pages = set()
random.seed(datetime.datetime.now())


# Retrieves a list of all Internal links found on a page
def getInternalLinks(bsObj, includeUrl):
    includeUrl = urlparse(includeUrl).scheme+"://"+urlparse(includeUrl).netloc
    internalLinks = []
    # Finds all links that begin with a "/"
    for link in bsObj.findAll("a", href=re.compile("^(/|.*"+includeUrl+")")):
        if link.attrs['href'] is not None:
            if link.attrs['href'] not in internalLinks:
                if(link.attrs['href'].startswith("/")):
                    internalLinks.append(includeUrl+link.attrs['href'])
                else:
                    internalLinks.append(link.attrs['href'])
    return internalLinks


# Retrieves a list of all external links found on a page
def getExternalLinks(bsObj, excludeUrl):
    externalLinks = []
    # Finds all links that start with "http" that do
    # not contain the current URL
    for link in bsObj.findAll("a", href=re.compile(
            "^(http|www)((?!"+excludeUrl+").)*$")):
        if link.attrs['href'] is not None:
            if link.attrs['href'] not in externalLinks:
                externalLinks.append(link.attrs['href'])
    return externalLinks


def getRandomExternalLink(startingPage):
    html = urlopen(startingPage)
    bsObj = BeautifulSoup(html)
    externalLinks = getExternalLinks(bsObj, urlparse(startingPage).netloc)
    if len(externalLinks) == 0:
        print("No external links, looking around the site for one")
        domain = urlparse(startingPage).scheme+"://" \
            + urlparse(startingPage).netloc
        internalLinks = getInternalLinks(bsObj, domain)
        return getRandomExternalLink(internalLinks[random.randint(0, len(internalLinks)-1)])
    else:
        return externalLinks[random.randint(0, len(externalLinks)-1)]


def followExternalOnly(startingSite):
    externalLink = getRandomExternalLink(startingSite)
    print("Random external link is: "+externalLink)
    followExternalOnly(externalLink)

if __name__ == "__main__":
    html = urlopen("https://www.xxxx.com.br")
    bsObj = BeautifulSoup(html, "lxml")
    links_to_crawl = crawler.getInternalLinks(bsObj, "https://www.xxxx.com.br")