Skip Montanaro's robots.txt parser.

1 files changed, 97 insertions, 0 deletions

diff --git a/Tools/webchecker/robotparser.py b/Tools/webchecker/robotparser.py
new file mode 100644
index 0000000..634c3fe
--- /dev/null
+++ b/Tools/webchecker/robotparser.py
@@ -0,0 +1,97 @@
+"""
+
+Robots.txt file parser class.  Accepts a list of lines or robots.txt URL as
+input, builds a set of rules from that list, then answers questions about
+fetchability of other URLs.
+
+"""
+
+class RobotFileParser:
+
+    def __init__(self):
+	self.rules = {}
+	self.debug = 0
+	self.url = ''
+	self.last_checked = 0
+
+    def mtime(self):
+	return self.last_checked
+
+    def modified(self):
+	import time
+	self.last_checked = time.time()
+
+    def set_url(self, url):
+	self.url = url
+## 	import urlmisc
+## 	self.url = urlmisc.canonical_url(url)
+
+    def read(self):
+	import urllib
+	self.parse(urllib.urlopen(self.url).readlines())
+
+    def parse(self, lines):
+	import regsub, string, regex
+	active = []
+	for line in lines:
+	    if self.debug: print '>', line,
+	    # blank line terminates current record
+	    if not line[:-1]:
+		active = []
+		continue
+	    # remove optional comment and strip line
+	    line = string.strip(line[:string.find(line, '#')])
+	    if not line:
+		continue
+	    line = regsub.split(line, ' *: *')
+	    if len(line) == 2:
+		line[0] = string.lower(line[0])
+		if line[0] == 'user-agent':
+		    # this record applies to this user agent
+		    if self.debug: print '>> user-agent:', line[1]
+		    active.append(line[1])
+		    if not self.rules.has_key(line[1]):
+			self.rules[line[1]] = []
+		elif line[0] == 'disallow':
+		    if line[1]:
+			if self.debug: print '>> disallow:', line[1]
+			for agent in active:
+			    self.rules[agent].append(regex.compile(line[1]))
+		    else:
+			pass
+			for agent in active:
+			    if self.debug: print '>> allow', agent
+			    self.rules[agent] = []
+		else:
+		    if self.debug: print '>> unknown:', line
+
+	self.modified()
+
+    # returns true if agent is allowed to fetch url
+    def can_fetch(self, agent, url):
+	import urlparse
+	ag = agent
+	if not self.rules.has_key(ag): ag = '*'
+	if not self.rules.has_key(ag):
+	    if self.debug: print '>> allowing', url, 'fetch by', agent
+	    return 1
+	path = urlparse.urlparse(url)[2]
+	for rule in self.rules[ag]:
+	    if rule.match(path) != -1:
+		if self.debug: print '>> disallowing', url, 'fetch by', agent
+		return 0
+	if self.debug: print '>> allowing', url, 'fetch by', agent
+	return 1
+
+def test():
+    rp = RobotFileParser()
+    rp.debug = 1
+    rp.set_url('http://www.automatrix.com/robots.txt')
+    rp.read()
+    print rp.rules
+    print rp.can_fetch('*', 'http://www.calendar.com/concerts/')
+    print rp.can_fetch('Musi-Cal-Robot',
+		       'http://dolphin:80/cgi-bin/music-search?performer=Rolling+Stones')
+
+    print rp.can_fetch('Lycos', 'http://www/~skip/volkswagen/')
+    print rp.can_fetch('Lycos', 'http://www/~skip/volkswagen/vanagon-list-001')