Making my own web crawler in python which shows main idea of the page rank

Question

I'm trying to make web crawler which shows basic idea of page rank. And code for me seems fine for me but gives me back errors e.x.

`Traceback (most recent call last):
  File "C:/Users/Janis/Desktop/WebCrawler/Web_crawler.py", line 89, in <module>
    webpages()
  File "C:/Users/Janis/Desktop/WebCrawler/Web_crawler.py", line 17, in webpages
    get_single_item_data(href)
  File "C:/Users/Janis/Desktop/WebCrawler/Web_crawler.py", line 23, in get_single_item_data
    source_code = requests.get(item_url)
  File "C:\Python34\lib\site-packages\requests\api.py", line 65, in get
    return request('get', url, **kwargs)
  File "C:\Python34\lib\site-packages\requests\api.py", line 49, in request
    response = session.request(method=method, url=url, **kwargs)
  File "C:\Python34\lib\site-packages\requests\sessions.py", line 447, in request
    prep = self.prepare_request(req)
  File "C:\Python34\lib\site-packages\requests\sessions.py", line 378, in prepare_request
    hooks=merge_hooks(request.hooks, self.hooks),
  File "C:\Python34\lib\site-packages\requests\models.py", line 303, in prepare
    self.prepare_url(url, params)
  File "C:\Python34\lib\site-packages\requests\models.py", line 360, in prepare_url
    "Perhaps you meant http://{0}?".format(url))
requests.exceptions.MissingSchema: Invalid URL '//www.hm.com/lv/logout': No schema supplied. Perhaps you meant http:////www.hm.com/lv/logout?`

and the last row of code which python gives me back after I run it is:

//www.hm.com/lv/logout

Maybe problem is with two // but I'm sure, anyway when I try to crall other web pages e.x. http://en.wikipedia.org/wiki/Wiki it gives me back None and same errors.

    import requests
    from bs4 import BeautifulSoup
    from collections import defaultdict
    from operator import itemgetter

    all_links = defaultdict(int)

    def webpages():

            url = 'http://www.hm.com/lv/'
            source_code = requests.get(url)
            text = source_code.text
            soup = BeautifulSoup(text)
            for link in soup.findAll ('a'):
                href = link.get('href')
                print(href)
                get_single_item_data(href)
            return all_links

    def get_single_item_data(item_url):
        #if not item_url.startswith('http'):
            #item_url = 'http' + item_url
        source_code = requests.get(item_url)
        text = source_code.text
        soup = BeautifulSoup(text)
        for link in soup.findAll('a'):
            href = link.get('href')
            if href and href.startswith('http://www.'):
                if href:
                    all_links[href] += 1
                print(href)

    def sort_algorithm(list):
        for index in range(1,len(list)):
            value= list[index]
            i = index - 1
            while i>=0:
                if value < list[i]:
                    list[i+1] = list[i]
                    list[i] = value
                    i=i -1
                else:
                    break

    vieni = ["", "viens", "divi", "tris", "cetri", "pieci",
             "sesi", "septini", "astoni", "devini"]
    padsmiti = ["", "vienpadsmit", "divpadsmit", "trispadsmit", "cetrpadsmit",
             "piecpadsmit", 'sespadsmit', "septinpadsmit", "astonpadsmit", "devinpadsmit"]
    desmiti = ["", "desmit", "divdesmit", "trisdesmit", "cetrdesmit",
            "piecdesmit", "sesdesmit", "septindesmit", "astondesmit", "devindesmit"]



    def num_to_words(n):
        words = []
        if n == 0:
            words.append("zero")
        else:
            num_str = "{}".format(n)
            groups = (len(num_str) + 2) // 3
            num_str = num_str.zfill(groups * 3)
            for i in range(0, groups * 3, 3):
                h = int(num_str[i])
                t = int(num_str[i + 1])
                u = int(num_str[i + 2])
                print()
                print(vieni[i])
                g = groups - (i // 3 + 1)
                if h >= 1:
                    words.append(vieni[h])
                    words.append("hundred")
                    if int(num_str) % 100:
                        words.append("and")
                if t > 1:
                    words.append(desmiti[t])
                    if u >= 1:
                        words.append(vieni[u])
                elif t == 1:
                    if u >= 1:
                        words.append(padsmiti[u])
                    else:
                        words.append(desmiti[t])
                else:
                    if u >= 1:
                        words.append(vieni[u])

        return " ".join(words)

    webpages()

    for k, v in sorted(webpages().items(),key=itemgetter(1),reverse=True):
        print(k, num_to_words(v))

Answer 1

The links come from the loop of webpages functions may be start with two slash.It means this link use the current Schema . For ex, open https://en.wikipedia.org/wiki/Wiki the link "//en.wikipedia.org/login" will be "https://en.wikipedia.org/login". open http://en.wikipedia.org/wiki/Wiki will be http://en.wikipedia.org/login.

A better way to open url in a html "a" tag is using the urlparse.urljoin function.It joins the target and current url. Regardless of absolute / relative path.

hope this can help u.