-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathspider01.py
More file actions
145 lines (121 loc) · 4.74 KB
/
spider01.py
File metadata and controls
145 lines (121 loc) · 4.74 KB
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
# -*- coding: utf-8 -*-
"""
Created on Mon Jan 08 15:31:10 2018
@author: yatop
"""
import re
import urlparse
import urllib2
import time
from datetime import datetime
import robotparser
import Queue
def link_crawler(seed_url, link_regex=None, delay=5, max_depth=-1, max_urls=-1, headers=None, user_agent='wswp', proxy=None, num_retries=1):
"""Crawl from the given seed URL following links matched by link_regex
"""
# the queue of URL's that still need to be crawled
crawl_queue = Queue.deque([seed_url])
# the URL's that have been seen and at what depth
seen = {seed_url: 0}
# track how many URL's have been downloaded
num_urls = 0
rp = get_robots(seed_url)
throttle = Throttle(delay)
headers = headers or {}
if user_agent:
headers['User-agent'] = user_agent
while crawl_queue:
url = crawl_queue.pop()
# check url passes robots.txt restrictions
if rp.can_fetch(user_agent, url):
throttle.wait(url)
html = download(url, headers, proxy=proxy, num_retries=num_retries)
links = []
depth = seen[url]
if depth != max_depth:
# can still crawl further
if link_regex:
# filter for links matching our regular expression
links.extend(link for link in get_links(html) if re.match(link_regex, link))
for link in links:
link = normalize(seed_url, link)
# check whether already crawled this link
if link not in seen:
seen[link] = depth + 1
# check link is within same domain
if same_domain(seed_url, link):
# success! add this new link to queue
crawl_queue.append(link)
# check whether have reached downloaded maximum
num_urls += 1
if num_urls == max_urls:
break
else:
print 'Blocked by robots.txt:', url
class Throttle:
"""Throttle downloading by sleeping between requests to same domain
"""
def __init__(self, delay):
# amount of delay between downloads for each domain
self.delay = delay
# timestamp of when a domain was last accessed
self.domains = {}
def wait(self, url):
domain = urlparse.urlparse(url).netloc
last_accessed = self.domains.get(domain)
if self.delay > 0 and last_accessed is not None:
sleep_secs = self.delay - (datetime.now() - last_accessed).seconds
if sleep_secs > 0:
time.sleep(sleep_secs)
self.domains[domain] = datetime.now()
def download(url, headers, proxy, num_retries, data=None):
print 'Downloading:', url
request = urllib2.Request(url, data, headers)
opener = urllib2.build_opener()
if proxy:
proxy_params = {urlparse.urlparse(url).scheme: proxy}
opener.add_handler(urllib2.ProxyHandler(proxy_params))
try:
response = opener.open(request)
html = response.read()
code = response.code
except urllib2.URLError as e:
print 'Download error:', e.reason
html = ''
if hasattr(e, 'code'):
code = e.code
if num_retries > 0 and 500 <= code < 600:
# retry 5XX HTTP errors
return download(url, headers, proxy, num_retries-1, data)
else:
code = None
return html
def normalize(seed_url, link):
"""Normalize this URL by removing hash and adding domain
"""
link, _ = urlparse.urldefrag(link) # remove hash to avoid duplicates
return urlparse.urljoin(seed_url, link)
def same_domain(url1, url2):
"""Return True if both URL's belong to same domain
"""
return urlparse.urlparse(url1).netloc == urlparse.urlparse(url2).netloc
def get_robots(url):
"""Initialize robots parser for this domain
"""
rp = robotparser.RobotFileParser()
rp.set_url(urlparse.urljoin(url, '/robots.txt'))
rp.read()
return rp
def get_links(html):
"""Return a list of links from html
"""
# a regular expression to extract all links from the webpage
webpage_regex = re.compile('<a[^>]+href=["\'](.*?)["\']', re.IGNORECASE)
# list of all links from the webpage
return webpage_regex.findall(html)
seed_url='http://example.webscraping.com/index'
link_regex='/places/default/(index|view)'
#link_crawler(seed_url,link_regex,max_depth=2)
#if __name__ == '__main__':
# link_crawler('http://example.webscraping.com', '/(index|view)', delay=0, num_retries=1, user_agent='BadCrawler')
# link_crawler('http://example.webscraping.com', '/(index|view)', delay=0, num_retries=1, max_depth=1)