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294 lines
9.9 KiB
Python
294 lines
9.9 KiB
Python
""" robotparser.py
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Copyright (C) 2000 Bastian Kleineidam
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You can choose between two licenses when using this package:
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1) GNU GPLv2
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2) PSF license for Python 2.2
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The robots.txt Exclusion Protocol is implemented as specified in
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http://info.webcrawler.com/mak/projects/robots/norobots-rfc.html
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"""
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import urlparse,urllib
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__all__ = ["RobotFileParser"]
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debug = 0
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def _debug(msg):
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if debug: print msg
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class RobotFileParser:
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""" This class provides a set of methods to read, parse and answer
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questions about a single robots.txt file.
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"""
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def __init__(self, url=''):
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self.entries = []
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self.default_entry = None
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self.disallow_all = False
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self.allow_all = False
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self.set_url(url)
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self.last_checked = 0
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def mtime(self):
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"""Returns the time the robots.txt file was last fetched.
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This is useful for long-running web spiders that need to
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check for new robots.txt files periodically.
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"""
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return self.last_checked
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def modified(self):
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"""Sets the time the robots.txt file was last fetched to the
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current time.
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"""
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import time
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self.last_checked = time.time()
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def set_url(self, url):
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"""Sets the URL referring to a robots.txt file."""
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self.url = url
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self.host, self.path = urlparse.urlparse(url)[1:3]
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def read(self):
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"""Reads the robots.txt URL and feeds it to the parser."""
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opener = URLopener()
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f = opener.open(self.url)
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lines = []
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line = f.readline()
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while line:
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lines.append(line.strip())
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line = f.readline()
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self.errcode = opener.errcode
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if self.errcode in (401, 403):
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self.disallow_all = True
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_debug("disallow all")
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elif self.errcode >= 400:
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self.allow_all = True
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_debug("allow all")
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elif self.errcode == 200 and lines:
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_debug("parse lines")
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self.parse(lines)
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def _add_entry(self, entry):
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if "*" in entry.useragents:
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# the default entry is considered last
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self.default_entry = entry
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else:
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self.entries.append(entry)
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def parse(self, lines):
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"""parse the input lines from a robots.txt file.
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We allow that a user-agent: line is not preceded by
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one or more blank lines."""
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state = 0
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linenumber = 0
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entry = Entry()
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for line in lines:
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linenumber = linenumber + 1
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if not line:
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if state==1:
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_debug("line %d: warning: you should insert"
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" allow: or disallow: directives below any"
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" user-agent: line" % linenumber)
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entry = Entry()
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state = 0
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elif state==2:
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self._add_entry(entry)
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entry = Entry()
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state = 0
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# remove optional comment and strip line
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i = line.find('#')
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if i>=0:
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line = line[:i]
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line = line.strip()
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if not line:
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continue
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line = line.split(':', 1)
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if len(line) == 2:
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line[0] = line[0].strip().lower()
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line[1] = urllib.unquote(line[1].strip())
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if line[0] == "user-agent":
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if state==2:
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_debug("line %d: warning: you should insert a blank"
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" line before any user-agent"
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" directive" % linenumber)
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self._add_entry(entry)
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entry = Entry()
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entry.useragents.append(line[1])
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state = 1
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elif line[0] == "disallow":
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if state==0:
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_debug("line %d: error: you must insert a user-agent:"
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" directive before this line" % linenumber)
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else:
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entry.rulelines.append(RuleLine(line[1], False))
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state = 2
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elif line[0] == "allow":
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if state==0:
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_debug("line %d: error: you must insert a user-agent:"
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" directive before this line" % linenumber)
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else:
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entry.rulelines.append(RuleLine(line[1], True))
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else:
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_debug("line %d: warning: unknown key %s" % (linenumber,
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line[0]))
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else:
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_debug("line %d: error: malformed line %s"%(linenumber, line))
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if state==2:
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self.entries.append(entry)
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_debug("Parsed rules:\n%s" % str(self))
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def can_fetch(self, useragent, url):
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"""using the parsed robots.txt decide if useragent can fetch url"""
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_debug("Checking robots.txt allowance for:\n user agent: %s\n url: %s" %
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(useragent, url))
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if self.disallow_all:
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return False
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if self.allow_all:
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return True
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# search for given user agent matches
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# the first match counts
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url = urllib.quote(urlparse.urlparse(urllib.unquote(url))[2]) or "/"
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for entry in self.entries:
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if entry.applies_to(useragent):
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return entry.allowance(url)
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# try the default entry last
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if self.default_entry:
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return self.default_entry.allowance(url)
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# agent not found ==> access granted
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return True
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def __str__(self):
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return ''.join([str(entry) + "\n" for entry in self.entries])
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class RuleLine:
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"""A rule line is a single "Allow:" (allowance==True) or "Disallow:"
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(allowance==False) followed by a path."""
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def __init__(self, path, allowance):
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if path == '' and not allowance:
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# an empty value means allow all
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allowance = True
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self.path = urllib.quote(path)
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self.allowance = allowance
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def applies_to(self, filename):
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return self.path=="*" or filename.startswith(self.path)
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def __str__(self):
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return (self.allowance and "Allow" or "Disallow")+": "+self.path
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class Entry:
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"""An entry has one or more user-agents and zero or more rulelines"""
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def __init__(self):
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self.useragents = []
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self.rulelines = []
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def __str__(self):
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ret = []
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for agent in self.useragents:
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ret.extend(["User-agent: ", agent, "\n"])
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for line in self.rulelines:
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ret.extend([str(line), "\n"])
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return ''.join(ret)
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def applies_to(self, useragent):
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"""check if this entry applies to the specified agent"""
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# split the name token and make it lower case
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useragent = useragent.split("/")[0].lower()
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for agent in self.useragents:
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if agent=='*':
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# we have the catch-all agent
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return True
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agent = agent.lower()
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if agent in useragent:
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return True
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return False
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def allowance(self, filename):
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"""Preconditions:
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- our agent applies to this entry
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- filename is URL decoded"""
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for line in self.rulelines:
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_debug((filename, str(line), line.allowance))
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if line.applies_to(filename):
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return line.allowance
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return True
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class URLopener(urllib.FancyURLopener):
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def __init__(self, *args):
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urllib.FancyURLopener.__init__(self, *args)
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self.errcode = 200
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def prompt_user_passwd(self, host, realm):
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## If robots.txt file is accessible only with a password,
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## we act as if the file wasn't there.
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return None, None
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def http_error_default(self, url, fp, errcode, errmsg, headers):
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self.errcode = errcode
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return urllib.FancyURLopener.http_error_default(self, url, fp, errcode,
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errmsg, headers)
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def _check(a,b):
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if not b:
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ac = "access denied"
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else:
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ac = "access allowed"
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if a!=b:
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print "failed"
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else:
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print "ok (%s)" % ac
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print
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def _test():
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global debug
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rp = RobotFileParser()
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debug = 1
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# robots.txt that exists, gotten to by redirection
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rp.set_url('http://www.musi-cal.com/robots.txt')
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rp.read()
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# test for re.escape
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_check(rp.can_fetch('*', 'http://www.musi-cal.com/'), 1)
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# this should match the first rule, which is a disallow
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_check(rp.can_fetch('', 'http://www.musi-cal.com/'), 0)
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# various cherry pickers
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_check(rp.can_fetch('CherryPickerSE',
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'http://www.musi-cal.com/cgi-bin/event-search'
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'?city=San+Francisco'), 0)
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_check(rp.can_fetch('CherryPickerSE/1.0',
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'http://www.musi-cal.com/cgi-bin/event-search'
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'?city=San+Francisco'), 0)
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_check(rp.can_fetch('CherryPickerSE/1.5',
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'http://www.musi-cal.com/cgi-bin/event-search'
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'?city=San+Francisco'), 0)
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# case sensitivity
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_check(rp.can_fetch('ExtractorPro', 'http://www.musi-cal.com/blubba'), 0)
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_check(rp.can_fetch('extractorpro', 'http://www.musi-cal.com/blubba'), 0)
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# substring test
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_check(rp.can_fetch('toolpak/1.1', 'http://www.musi-cal.com/blubba'), 0)
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# tests for catch-all * agent
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_check(rp.can_fetch('spam', 'http://www.musi-cal.com/search'), 0)
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_check(rp.can_fetch('spam', 'http://www.musi-cal.com/Musician/me'), 1)
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_check(rp.can_fetch('spam', 'http://www.musi-cal.com/'), 1)
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_check(rp.can_fetch('spam', 'http://www.musi-cal.com/'), 1)
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# robots.txt that does not exist
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rp.set_url('http://www.lycos.com/robots.txt')
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rp.read()
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_check(rp.can_fetch('Mozilla', 'http://www.lycos.com/search'), 1)
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if __name__ == '__main__':
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_test()
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