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Diffstat (limited to 'lib/python2.7/robotparser.py')
| -rw-r--r-- | lib/python2.7/robotparser.py | 222 |
1 files changed, 222 insertions, 0 deletions
diff --git a/lib/python2.7/robotparser.py b/lib/python2.7/robotparser.py new file mode 100644 index 0000000..1722863 --- /dev/null +++ b/lib/python2.7/robotparser.py @@ -0,0 +1,222 @@ +""" 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 +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: + 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() + + 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 + # 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): + return ''.join([str(entry) + "\n" for entry in self.entries]) + + +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.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) |