-
Notifications
You must be signed in to change notification settings - Fork 0
/
feedfinder.py
252 lines (200 loc) · 6.19 KB
/
feedfinder.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
"""
FeedFinder
==============
Tries to find feeds for
a given URL.
This is essentially a rewrite
of feedfinder.py,
originally by Mark Pilgrim
and Aaron Swartz.
Credits from the original:
Abe Fettig for a patch to sort Syndic8 feeds by popularity
Also Jason Diamond, Brian Lalor for bug reporting and patches
Original is located at:
http://www.aaronsw.com/2002/feedfinder/
How it works:
0. At every step, feeds are minimally verified to make sure they are really feeds.
1. If the URI points to a feed, it is simply returned; otherwise
the page is downloaded and the real fun begins.
2. Feeds pointed to by LINK tags in the header of the page (autodiscovery)
3. <A> links to feeds on the same server ending in ".rss", ".rdf", ".xml", or
".atom"
4. <A> links to feeds on the same server containing "rss", "rdf", "xml", or "atom"
5. Try some guesses about common places for feeds (index.xml, atom.xml, etc.).
6. <A> links to feeds on external servers ending in ".rss", ".rdf", ".xml", or
".atom"
7. <A> links to feeds on external servers containing "rss", "rdf", "xml", or "atom"
Copyright:
2002-2004: Mark Pilgrim
2006: Aaron Swartz
2013: Francis Tseng
"""
# Python 2.7 support.
try:
from urllib import request, parse
except ImportError:
import urllib2 as request
import urlparse as parse
import lxml.html
import chardet
def feeds(url):
"""
Tries to find feeds
for a given URL.
"""
url = _full_url(url)
data = _get(url)
# Check if the url is a feed.
if _is_feed(url):
return [url]
# Try to get feed links from markup.
try:
feed_links = [link for link in _get_feed_links(data, url) if _is_feed(link)]
except:
feed_links = []
if feed_links:
return feed_links
# Try 'a' links.
try:
links = _get_a_links(data)
except:
links = []
if links:
# Filter to only local links.
local_links = [link for link in links if link.startswith(url)]
# Try to find feed links.
feed_links.extend(_filter_feed_links(local_links))
# If still nothing has been found...
if not feed_links:
# Try to find feed-looking links.
feed_links.extend(_filter_feedish_links(local_links))
# If still nothing has been found...
if not feed_links:
# BRUTE FORCE IT!
guesses = [
'atom.xml', # Blogger, TypePad
'index.atom', # MoveableType
'index.rdf', # MoveableType
'rss.xml', # Dave Winer/Manila
'index.xml', # MoveableType
'index.rss', # Slash
'feed' # WordPress
]
tries = [parse.urljoin(url, g) for g in guesses]
feed_links.extend([link for link in tries if _is_feed(link)])
# If *still* nothing has been found,
# just try all the links.
if links and not feed_links:
feed_links.extend(_filter_feed_links(links))
feed_links.extend(_filter_feedish_links(links))
# Filter out duplicates.
return list(set(feed_links))
def feed(url):
feed_links = feeds(url)
if feed_links:
return feed_links[0]
else:
return None
def _full_url(url):
"""
Assemble the full url
for a url.
"""
url = url.strip()
for x in ['http', 'https']:
if url.startswith('%s://' % x):
return url
return 'http://%s' % url
def _get_feed_links(data, url):
"""
Try to get feed links
defined in the markup.
"""
FEED_TYPES = ('application/rss+xml',
'text/xml',
'application/atom+xml',
'application/x.atom+xml',
'application/x-atom+xml')
links = []
html = lxml.html.fromstring(data)
# For each link...
for link in html.xpath('//link'):
# Try to get the 'rel' attribute.
rel = link.attrib.get('rel', False)
href = link.attrib.get('href', False)
type = link.attrib.get('type', False)
# Check some things.
if not rel or not href or not type: continue
if 'alternate' not in rel.split(): continue
if type not in FEED_TYPES: continue
links.append(parse.urljoin(url, href))
return links
def _get_a_links(data):
"""
Gathers all 'a' links
from the markup.
"""
html = lxml.html.fromstring(data)
return html.xpath('//a/@href')
def _is_feed(url):
"""
Test if a given URL is
a feed.
"""
# If it's not HTTP or HTTPS,
# it's not a feed.
scheme = parse.urlparse(url).scheme
if scheme not in ('http', 'https'):
return 0
data = _get(url)
# If an html tag is present,
# assume it's not a feed.
if data.count('<html'):
return 0
return data.count('<rss') + data.count('<rdf') + data.count('<feed')
def _is_feed_link(url):
"""
Check if a link is
a feed link.
"""
return url[-4:] in ('.rss', '.rdf', '.xml', '.atom')
def _filter_feed_links(links):
"""
Filters a list of links
for only feed links.
"""
candidates = [link for link in links if _is_feed_link(link)]
return [link for link in candidates if _is_feed(link)]
def _filter_feedish_links(links):
"""
Filters a list of links
for links that *look* like
they may be feed links.
"""
feed_links = []
for link in links:
if link.count('rss') + link.count('rdf') + link.count('xml') + link.count('atom'):
if _is_feed(link):
feed_links.append(link)
return feed_links
def _get(url):
"""
Tries to access the url
and return its data.
"""
req = request.Request(url)
try:
resp = request.urlopen(req)
body = resp.read()
# Use Chardet to determine the encoding.
encoding = chardet.detect(body)['encoding']
return body.decode(encoding)
except request.HTTPError as e:
print('HTTP Error:', e.code, url)
return ''
except request.URLError as e:
print('URL Error:', e.reason, url)
return ''
except ConnectionResetError as e:
print('Connection Error:', e.reason, url)
return ''