| 1 | """ robotparser.py
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| 2 |
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| 3 | Copyright (C) 2000 Bastian Kleineidam
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| 4 |
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| 5 | You can choose between two licenses when using this package:
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| 6 | 1) GNU GPLv2
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| 7 | 2) PSF license for Python 2.2
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| 8 |
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| 9 | The robots.txt Exclusion Protocol is implemented as specified in
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| 10 | http://info.webcrawler.com/mak/projects/robots/norobots-rfc.html
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| 11 | """
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| 12 | import urlparse
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| 13 | import urllib
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| 14 |
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| 15 | __all__ = ["RobotFileParser"]
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| 16 |
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| 17 |
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| 18 | class RobotFileParser:
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| 19 | """ This class provides a set of methods to read, parse and answer
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| 20 | questions about a single robots.txt file.
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| 21 |
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| 22 | """
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| 23 |
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| 24 | def __init__(self, url=''):
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| 25 | self.entries = []
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| 26 | self.default_entry = None
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| 27 | self.disallow_all = False
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| 28 | self.allow_all = False
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| 29 | self.set_url(url)
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| 30 | self.last_checked = 0
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| 31 |
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| 32 | def mtime(self):
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| 33 | """Returns the time the robots.txt file was last fetched.
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| 34 |
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| 35 | This is useful for long-running web spiders that need to
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| 36 | check for new robots.txt files periodically.
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| 37 |
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| 38 | """
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| 39 | return self.last_checked
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| 40 |
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| 41 | def modified(self):
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| 42 | """Sets the time the robots.txt file was last fetched to the
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| 43 | current time.
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| 44 |
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| 45 | """
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| 46 | import time
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| 47 | self.last_checked = time.time()
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| 48 |
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| 49 | def set_url(self, url):
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| 50 | """Sets the URL referring to a robots.txt file."""
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| 51 | self.url = url
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| 52 | self.host, self.path = urlparse.urlparse(url)[1:3]
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| 53 |
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| 54 | def read(self):
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| 55 | """Reads the robots.txt URL and feeds it to the parser."""
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| 56 | opener = URLopener()
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| 57 | f = opener.open(self.url)
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| 58 | lines = [line.strip() for line in f]
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| 59 | f.close()
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| 60 | self.errcode = opener.errcode
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| 61 | if self.errcode in (401, 403):
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| 62 | self.disallow_all = True
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| 63 | elif self.errcode >= 400:
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| 64 | self.allow_all = True
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| 65 | elif self.errcode == 200 and lines:
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| 66 | self.parse(lines)
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| 67 |
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| 68 | def _add_entry(self, entry):
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| 69 | if "*" in entry.useragents:
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| 70 | # the default entry is considered last
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| 71 | self.default_entry = entry
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| 72 | else:
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| 73 | self.entries.append(entry)
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| 74 |
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| 75 | def parse(self, lines):
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| 76 | """parse the input lines from a robots.txt file.
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| 77 | We allow that a user-agent: line is not preceded by
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| 78 | one or more blank lines."""
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| 79 | # states:
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| 80 | # 0: start state
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| 81 | # 1: saw user-agent line
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| 82 | # 2: saw an allow or disallow line
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| 83 | state = 0
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| 84 | linenumber = 0
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| 85 | entry = Entry()
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| 86 |
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| 87 | for line in lines:
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| 88 | linenumber += 1
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| 89 | if not line:
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| 90 | if state == 1:
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| 91 | entry = Entry()
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| 92 | state = 0
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| 93 | elif state == 2:
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| 94 | self._add_entry(entry)
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| 95 | entry = Entry()
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| 96 | state = 0
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| 97 | # remove optional comment and strip line
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| 98 | i = line.find('#')
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| 99 | if i >= 0:
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| 100 | line = line[:i]
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| 101 | line = line.strip()
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| 102 | if not line:
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| 103 | continue
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| 104 | line = line.split(':', 1)
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| 105 | if len(line) == 2:
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| 106 | line[0] = line[0].strip().lower()
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| 107 | line[1] = urllib.unquote(line[1].strip())
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| 108 | if line[0] == "user-agent":
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| 109 | if state == 2:
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| 110 | self._add_entry(entry)
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| 111 | entry = Entry()
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| 112 | entry.useragents.append(line[1])
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| 113 | state = 1
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| 114 | elif line[0] == "disallow":
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| 115 | if state != 0:
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| 116 | entry.rulelines.append(RuleLine(line[1], False))
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| 117 | state = 2
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| 118 | elif line[0] == "allow":
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| 119 | if state != 0:
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| 120 | entry.rulelines.append(RuleLine(line[1], True))
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| 121 | state = 2
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| 122 | if state == 2:
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| 123 | self.entries.append(entry)
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| 124 |
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| 125 |
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| 126 | def can_fetch(self, useragent, url):
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| 127 | """using the parsed robots.txt decide if useragent can fetch url"""
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| 128 | if self.disallow_all:
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| 129 | return False
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| 130 | if self.allow_all:
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| 131 | return True
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| 132 | # search for given user agent matches
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| 133 | # the first match counts
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| 134 | url = urllib.quote(urlparse.urlparse(urllib.unquote(url))[2]) or "/"
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| 135 | for entry in self.entries:
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| 136 | if entry.applies_to(useragent):
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| 137 | return entry.allowance(url)
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| 138 | # try the default entry last
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| 139 | if self.default_entry:
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| 140 | return self.default_entry.allowance(url)
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| 141 | # agent not found ==> access granted
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| 142 | return True
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| 143 |
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| 144 |
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| 145 | def __str__(self):
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| 146 | return ''.join([str(entry) + "\n" for entry in self.entries])
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| 147 |
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| 148 |
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| 149 | class RuleLine:
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| 150 | """A rule line is a single "Allow:" (allowance==True) or "Disallow:"
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| 151 | (allowance==False) followed by a path."""
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| 152 | def __init__(self, path, allowance):
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| 153 | if path == '' and not allowance:
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| 154 | # an empty value means allow all
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| 155 | allowance = True
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| 156 | self.path = urllib.quote(path)
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| 157 | self.allowance = allowance
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| 158 |
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| 159 | def applies_to(self, filename):
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| 160 | return self.path == "*" or filename.startswith(self.path)
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| 161 |
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| 162 | def __str__(self):
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| 163 | return (self.allowance and "Allow" or "Disallow") + ": " + self.path
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| 164 |
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| 165 |
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| 166 | class Entry:
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| 167 | """An entry has one or more user-agents and zero or more rulelines"""
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| 168 | def __init__(self):
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| 169 | self.useragents = []
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| 170 | self.rulelines = []
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| 171 |
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| 172 | def __str__(self):
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| 173 | ret = []
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| 174 | for agent in self.useragents:
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| 175 | ret.extend(["User-agent: ", agent, "\n"])
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| 176 | for line in self.rulelines:
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| 177 | ret.extend([str(line), "\n"])
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| 178 | return ''.join(ret)
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| 179 |
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| 180 | def applies_to(self, useragent):
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| 181 | """check if this entry applies to the specified agent"""
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| 182 | # split the name token and make it lower case
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| 183 | useragent = useragent.split("/")[0].lower()
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| 184 | for agent in self.useragents:
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| 185 | if agent == '*':
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| 186 | # we have the catch-all agent
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| 187 | return True
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| 188 | agent = agent.lower()
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| 189 | if agent in useragent:
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| 190 | return True
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| 191 | return False
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| 192 |
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| 193 | def allowance(self, filename):
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| 194 | """Preconditions:
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| 195 | - our agent applies to this entry
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| 196 | - filename is URL decoded"""
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| 197 | for line in self.rulelines:
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| 198 | if line.applies_to(filename):
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| 199 | return line.allowance
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| 200 | return True
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| 201 |
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| 202 | class URLopener(urllib.FancyURLopener):
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| 203 | def __init__(self, *args):
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| 204 | urllib.FancyURLopener.__init__(self, *args)
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| 205 | self.errcode = 200
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| 206 |
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| 207 | def prompt_user_passwd(self, host, realm):
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| 208 | ## If robots.txt file is accessible only with a password,
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| 209 | ## we act as if the file wasn't there.
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| 210 | return None, None
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| 211 |
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| 212 | def http_error_default(self, url, fp, errcode, errmsg, headers):
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| 213 | self.errcode = errcode
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| 214 | return urllib.FancyURLopener.http_error_default(self, url, fp, errcode,
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| 215 | errmsg, headers)
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