| """ 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() |
