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Use lxml if available and parse head only. #10

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Use lxml if available and parse head only. #10

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39 changes: 28 additions & 11 deletions extraction/techniques.py
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Original file line number Diff line number Diff line change
@@ -1,9 +1,26 @@
"This file contains techniques for extracting data from HTML pages."
import bs4

LXML_AVAILABLE = False

def init_bs(html):
return bs4.BeautifulSoup(html, features="html5lib")
try:
import lxml
LXML_AVAILABLE = True
except ImportError:
pass


def init_bs(html, head_only=False):
features = "html5lib"
parse_only = None

if LXML_AVAILABLE:
features = "lxml"

if head_only:
parse_only = bs4.SoupStrainer("head")

return bs4.BeautifulSoup(html, features=features, parse_only=parse_only)


class Technique(object):
Expand All @@ -14,7 +31,7 @@ def __init__(self, extractor=None, *args, **kwargs):
"""
self.extractor = extractor
super(Technique, self).__init__(*args, **kwargs)

def extract(self, html):
"Extract data from a string representing an HTML document."
return {'titles': [],
Expand Down Expand Up @@ -48,7 +65,7 @@ class HeadTags(Technique):
def extract(self, html):
"Extract data from meta, link and title tags within the head tag."
extracted = {}
soup = init_bs(html)
soup = init_bs(html, head_only=True)
# extract data from title tag
title_tag = soup.find('title')
if title_tag:
Expand Down Expand Up @@ -114,7 +131,7 @@ class FacebookOpengraphTags(Technique):
def extract(self, html):
"Extract data from Facebook Opengraph tags."
extracted = {}
soup = init_bs(html)
soup = init_bs(html, head_only=True)
for meta_tag in soup.find_all('meta'):
if self.key_attr in meta_tag.attrs and 'content' in meta_tag.attrs:
property = meta_tag[self.key_attr]
Expand Down Expand Up @@ -144,7 +161,7 @@ class HTML5SemanticTags(Technique):
The HTML5 `article` tag, and also the `video` tag give us some useful
hints for extracting page information for the sites which happen to
utilize these tags.

This technique will extract information from pages formed like::

<html>
Expand All @@ -166,7 +183,7 @@ class HTML5SemanticTags(Technique):
of cases where it hits, and otherwise expects `SemanticTags` to run sweep
behind it for the lower quality, more abundant hits it discovers.
"""

def extract(self, html):
"Extract data from HTML5 semantic tags."
titles = []
Expand Down Expand Up @@ -207,12 +224,12 @@ class SemanticTags(Technique):
]
# format is ("name of tag", "destination list", "name of attribute" store_first_n)
extract_attr = [('img', 'images', 'src', 10)]

def extract(self, html):
"Extract data from usual semantic tags."
extracted = {}
soup = init_bs(html)

for tag, dest, max_to_store in self.extract_string:
for found in soup.find_all(tag)[:max_to_store] or []:
if dest not in extracted:
Expand All @@ -227,5 +244,5 @@ def extract(self, html):
extracted[dest].append(found[attribute])

return extracted