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"""
Robots.txt file parser class. Accepts a list of lines or robots.txt URL as
input, builds a set of rules from that list, then answers questions about
fetchability of other URLs.
"""
class RobotFileParser:
def __init__(self):
self.rules = {}
self.debug = 0
self.url = ''
self.last_checked = 0
def mtime(self):
return self.last_checked
def modified(self):
import time
self.last_checked = time.time()
def set_url(self, url):
self.url = url
def read(self):
import urllib
self.parse(urllib.urlopen(self.url).readlines())
def parse(self, lines):
"""parse the input lines from a robot.txt file"""
import string, re
active = []
for line in lines:
if self.debug: print '>', line,
# blank line terminates current record
if not line[:-1]:
active = []
continue
# remove optional comment and strip line
line = string.strip(line[:string.find(line, '#')])
if not line:
continue
line = re.split(' *: *', line)
if len(line) == 2:
line[0] = string.lower(line[0])
if line[0] == 'user-agent':
# this record applies to this user agent
if self.debug: print '>> user-agent:', line[1]
active.append(line[1])
if not self.rules.has_key(line[1]):
self.rules[line[1]] = []
elif line[0] == 'disallow':
if line[1]:
if self.debug: print '>> disallow:', line[1]
for agent in active:
self.rules[agent].append(re.compile(line[1]))
else:
pass
for agent in active:
if self.debug: print '>> allow', agent
self.rules[agent] = []
else:
if self.debug: print '>> unknown:', line
self.modified()
# returns true if agent is allowed to fetch url
def can_fetch(self, useragent, url):
"""using the parsed robots.txt decide if useragent can fetch url"""
import urlparse
ag = useragent
if not self.rules.has_key(ag): ag = '*'
if not self.rules.has_key(ag):
if self.debug: print '>> allowing', url, 'fetch by', useragent
return 1
path = urlparse.urlparse(url)[2]
for rule in self.rules[ag]:
if rule.match(path) is not None:
if self.debug: print '>> disallowing', url, 'fetch by', useragent
return 0
if self.debug: print '>> allowing', url, 'fetch by', useragent
return 1
def _test():
rp = RobotFileParser()
rp.debug = 1
rp.set_url('http://www.musi-cal.com/robots.txt')
rp.read()
print rp.rules
print rp.can_fetch('*', 'http://www.musi-cal.com.com/')
print rp.can_fetch('Musi-Cal-Robot',
'http://www.musi-cal.com/cgi-bin/event-search?city=San+Francisco')
if __name__ == "__main__":
_test()
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