| """ 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://www.robotstxt.org/norobots-rfc.txt |
| |
| """ |
| import urlparse |
| import urllib |
| |
| __all__ = ["RobotFileParser"] |
| |
| |
| 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.strip() for line in f] |
| f.close() |
| self.errcode = opener.errcode |
| if self.errcode in (401, 403): |
| self.disallow_all = True |
| elif self.errcode >= 400 and self.errcode < 500: |
| self.allow_all = True |
| elif self.errcode == 200 and lines: |
| self.parse(lines) |
| |
| def _add_entry(self, entry): |
| if "*" in entry.useragents: |
| # the default entry is considered last |
| if self.default_entry is None: |
| # the first default entry wins |
| 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.""" |
| # states: |
| # 0: start state |
| # 1: saw user-agent line |
| # 2: saw an allow or disallow line |
| state = 0 |
| linenumber = 0 |
| entry = Entry() |
| |
| self.modified() |
| for line in lines: |
| linenumber += 1 |
| if not line: |
| if state == 1: |
| 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: |
| self._add_entry(entry) |
| entry = Entry() |
| entry.useragents.append(line[1]) |
| state = 1 |
| elif line[0] == "disallow": |
| if state != 0: |
| entry.rulelines.append(RuleLine(line[1], False)) |
| state = 2 |
| elif line[0] == "allow": |
| if state != 0: |
| entry.rulelines.append(RuleLine(line[1], True)) |
| state = 2 |
| if state == 2: |
| self._add_entry(entry) |
| |
| |
| def can_fetch(self, useragent, url): |
| """using the parsed robots.txt decide if useragent can fetch url""" |
| if self.disallow_all: |
| return False |
| if self.allow_all: |
| return True |
| |
| # Until the robots.txt file has been read or found not |
| # to exist, we must assume that no url is allowable. |
| # This prevents false positives when a user erroneously |
| # calls can_fetch() before calling read(). |
| if not self.last_checked: |
| return False |
| |
| # search for given user agent matches |
| # the first match counts |
| parsed_url = urlparse.urlparse(urllib.unquote(url)) |
| url = urlparse.urlunparse(('', '', parsed_url.path, |
| parsed_url.params, parsed_url.query, parsed_url.fragment)) |
| url = urllib.quote(url) |
| if not url: |
| url = "/" |
| 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): |
| entries = self.entries |
| if self.default_entry is not None: |
| entries = entries + [self.default_entry] |
| return '\n'.join(map(str, entries)) + '\n' |
| |
| |
| 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 |
| path = urlparse.urlunparse(urlparse.urlparse(path)) |
| 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.extend(["User-agent: ", agent, "\n"]) |
| for line in self.rulelines: |
| ret.extend([str(line), "\n"]) |
| return ''.join(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: |
| 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) |
