Hi,
I’m new to programming. I’m currently learning python to write a web crawler to
extract all text from a web page, in addition to, crawling to further URLs and
collecting the text there. The idea is to place all the extracted text in a
.txt file with each word in a single line. So the text has to be tokenized. All
punctuation marks, duplicate words and non-stop words have to be removed.
The program should crawl the web to a certain depth and collect the URLs and
text from each depth (level). I decided to choose a depth of 3. I divided the
code to two parts. Part one to collect the URLs and part two to extract the
text. Here is my problem:
1. The program is extremely slow.
2. I'm not sure if it functions properly.
3. Is there a better way to extract text?
4. Are there any available modules to help clean the text i.e. removing
duplicates, non-stop words ...
5. Any suggestions or feedback is appreciated.
(Please Note: the majority of the code (the first part) is written by “James
Mills”. I found the code online and it looks helpful so I used it. I just
modified it and added my code to it)
Thanks,
Kal
import sys
import urllib2
import urlparse
from BeautifulSoup import BeautifulSoup,NavigableString
__version__ = "0.1"
__copyright__ = "CopyRight (C) 2008 by James Mills"
__license__ = "GPL"
__author__ = "James Mills"
__author_email__ = "James Mills, James dot Mills st dotred dot com dot au"
USAGE = "%prog [options] <url>"
VERSION = "%prog v" + __version__
AGENT = "%s/%s" % (__name__, __version__)
def encodeHTML(s=""):
"""encodeHTML(s) -> str
Encode HTML special characters from their ASCII form to
HTML entities.
"""
return s.replace("&", "&") \
.replace("<", "<") \
.replace(">", ">") \
.replace("\"", """) \
.replace("'", "'") \
.replace("--", "&mdash")
class Fetcher(object):
def __init__(self, url):
self.url = url
self.urls = []
def __contains__(self, x):
return x in self.urls
def __getitem__(self, x):
return self.urls[x]
def _addHeaders(self, request):
request.add_header("User-Agent", AGENT)
def open(self):
url = self.url
#print "\nFollowing %s" % url
try:
request = urllib2.Request(url)
handle = urllib2.build_opener()
except IOError:
return None
return (request, handle)
def fetch(self):
request, handle = self.open()
self._addHeaders(request)
if handle:
soup = BeautifulSoup()
try:
content = unicode(handle.open(request).read(), errors="ignore")
soup.feed(content)
#soup = BeautifulSoup(content)
tags = soup('a')
except urllib2.HTTPError, error:
if error.code == 404:
print >> sys.stderr, "ERROR: %s -> %s" % (error, error.url)
else:
print >> sys.stderr, "ERROR: %s" % error
tags = []
except urllib2.URLError, error:
print >> sys.stderr, "ERROR: %s" % error
tags = []
for tag in tags:
try:
href = tag["href"]
if href is not None:
url = urlparse.urljoin(self.url, encodeHTML(href))
if url not in self:
#print " Found: %s" % url
self.urls.append(url)
except KeyError:
pass
################################################################################
# I created 3 lists (root, level2 and level3). #
# Each list saves the URLs of that level i.e. depth. I choose to create 3 #
# lists so I can have the flexibility of testing the text in each level. Also, #
# the 3 lists can be easily combined into one list. #
################################################################################
# Level1:
root = Fetcher('http://www.wantasimplewebsite.co.uk/index.html')
root.fetch()
for url in root:
if url not in root: # Avoid duplicate links
root.append(url)
print "\nRoot URLs are:"
for i, url in enumerate(root):
print "%d. %s" % (i+1, url)
# Level2:
level2 = []
for url in root: # Traverse every element(i.e URL) in root and fetch the URLs
from it
temp = Fetcher(url)
temp.fetch()
for url in temp:
if url not in level2: # Avoid duplicate links
level2.append(url)
print "\nLevel2 URLs are:"
for i, url in enumerate(level2):
print "%d. %s" % (i+1, url)
# Level3:
level3 = []
for url in level2: # Traverse every element(i.e URL) in level2 and fetch the
URLs from it
temp = Fetcher(url)
temp.fetch()
for url in temp:
if url not in level3: # Avoid duplicate links
level3.append(url)
print "\nLevel3 URLs are:"
for i, url in enumerate(level3):
print "%d. %s" % (i+1, url)
# 1. Traverse every link in the lists and extract its web page content.
# 2. Tokenize Text.
# 3. Remove stop-words (i.e. and, but, to...)
# 4. Remove duplicates
# 5. What about stemming?
# 6. Check the spelling.
# 7. Save the result in a file
html = urllib2.urlopen('http://www.wantasimplewebsite.co.uk/index.html').read()
soup = BeautifulSoup(html)
def printText(tags):
for tag in tags:
if tag.__class__ == NavigableString:
print tag,
else:
printText(tag)
printText(soup.findAll("body"))
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