simple web crawler

Question

i wrote below program in python for very simple web crawler, but when i run it it return me 'NoneType' object is not callable' , could you please help me?

import BeautifulSoup
import urllib2
def union(p,q):
    for e in q:
        if e not in p:
            p.append(e)

def crawler(SeedUrl):
    tocrawl=[SeedUrl]
    crawled=[]
    while tocrawl:
        page=tocrawl.pop()
        pagesource=urllib2.urlopen(page)
        s=pagesource.read()
        soup=BeautifulSoup.BeautifulSoup(s)
        links=soup('a')        
        if page not in crawled:
            union(tocrawl,links)
            crawled.append(page)

    return crawled
crawler('http://www.princeton.edu/main/')

Can you post the full traceback? That should at least narrow down what function call is being made on a `None` value. — Blckknght, Dec 01 '12 at 11:32

score 6 · Answer 1 · edited May 23 '17 at 12:01

[UPDATE] Here is the complete project code

https://bitbucket.org/deshan/simple-web-crawler

[ANWSER]

soup('a') returns the complete html tag.

<a href="http://itunes.apple.com/us/store">Buy Music Now</a>

so the urlopen gives the error 'NoneType' object is not callable'. you need extract the only the url/href.

links=soup.findAll('a',href=True)
for l in links:
    print(l['href'])

You need to validate the url too.refer to following anwsers

Again i would like to suggest you to use python sets instead Arrays.you can easily add,ommit duplicate urls.

http://docs.python.org/2/library/sets.html

Try the following code:

import re
import httplib
import urllib2
from urlparse import urlparse
import BeautifulSoup

regex = re.compile(
        r'^(?:http|ftp)s?://' # http:// or https://
        r'(?:(?:[A-Z0-9](?:[A-Z0-9-]{0,61}[A-Z0-9])?\.)+(?:[A-Z]{2,6}\.?|[A-Z0-9-]{2,}\.?)|' #domain...
        r'localhost|' #localhost...
        r'\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})' # ...or ip
        r'(?::\d+)?' # optional port
        r'(?:/?|[/?]\S+)$', re.IGNORECASE)

def isValidUrl(url):
    if regex.match(url) is not None:
        return True;
    return False

def crawler(SeedUrl):
    tocrawl=[SeedUrl]
    crawled=[]
    while tocrawl:
        page=tocrawl.pop()
        print 'Crawled:'+page
        pagesource=urllib2.urlopen(page)
        s=pagesource.read()
        soup=BeautifulSoup.BeautifulSoup(s)
        links=soup.findAll('a',href=True)        
        if page not in crawled:
            for l in links:
                if isValidUrl(l['href']):
                    tocrawl.append(l['href'])
            crawled.append(page)   
    return crawled
crawler('http://www.princeton.edu/main/')

simple web crawler

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