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