Added new exception classes:

NNTPError - derived from Exception, it's the base class for all
    other exceptions in this module

    NNTPReplyError - what used to be error_reply

    NNTPTemporaryError - what used to be error_temp

    NNTPPermanentError - what used to be error_perm

    NNTPProtocolError - what used to be error_proto

    NNTPDataError - what used to be error_data

All the old names are retained for backwards compatibility; they point
to the class that replaces them.  Also, any code in this module that
raises an exception, now does so with the exception class.

NNTP.__init__(): Added a new optional argument `readermode', which is
a flag that defaults to false.  When set to true, the "mode reader"
command is sent to the NNTP server before user authentication.  Reader
mode is sometimes necessary if you are connecting to an NNTP server on
the local machine and intend to call reader-specific comamnds, such as
`group'.  If you get unexpected NNTPPermanentErrors, you might need to
set readermode.  Patch provided by Thomas Wouters (who include the
standard disclaimer on is patches@python.org submission), and inspired
by Jim Tittsler.

Lib/nntplib.py

@@ -34,14 +34,46 @@ import socket
 import string
 
 
-# Exception raised when an error or invalid response is received
-error_reply = 'nntplib.error_reply'	# unexpected [123]xx reply
-error_temp = 'nntplib.error_temp'	# 4xx errors
-error_perm = 'nntplib.error_perm'	# 5xx errors
-error_proto = 'nntplib.error_proto'	# response does not begin with [1-5]
-error_data = 'nntplib.error_data'	# error in response data
+
+# Exceptions raised when an error or invalid response is received
+class NNTPError(Exception):
+	"""Base class for all nntplib exceptions"""
+	def __init__(self, *args):
+		apply(Exception.__init__, (self,)+args)
+		try:
+			self.response = args[0]
+		except IndexError:
+			self.response = 'No response given'
+
+class NNTPReplyError(NNTPError):
+	"""Unexpected [123]xx reply"""
+	pass
+
+class NNTPTemporaryError(NNTPError):
+	"""4xx errors"""
+	pass
+
+class NNTPPermanentError(NNTPError):
+	"""5xx errors"""
+	pass
+
+class NNTPProtocolError(NNTPError):
+	"""Response does not begin with [1-5]"""
+	pass
+
+class NNTPDataError(NNTPError):
+	"""Error in response data"""
+	pass
+
+# for backwards compatibility
+error_reply = NNTPReplyError
+error_temp = NNTPTemporaryError
+error_perm = NNTPPermanentError
+error_proto = NNTPProtocolError
+error_data = NNTPDataError
 
 
+
 # Standard port used by NNTP servers
 NNTP_PORT = 119
 
@@ -54,15 +86,25 @@ LONGRESP = ['100', '215', '220', '221', '222', '224', '230', '231', '282']
 CRLF = '\r\n'
 
 
+
 # The class itself
-
 class NNTP:
-
-	def __init__(self, host, port = NNTP_PORT, user=None, password=None):
+	def __init__(self, host, port=NNTP_PORT, user=None, password=None,
+		     readermode=None):
 		"""Initialize an instance.  Arguments:
 		- host: hostname to connect to
-		- port: port to connect to (default the standard NNTP port)"""
+		- port: port to connect to (default the standard NNTP port)
+		- user: username to authenticate with
+		- password: password to use with username
+		- readermode: if true, send 'mode reader' command after
+		              connecting.
 
+	        readermode is sometimes necessary if you are connecting to an
+	        NNTP server on the local machine and intend to call
+	        reader-specific comamnds, such as `group'.  If you get
+	        unexpected NNTPPermanentErrors, you might need to set
+	        readermode.
+		"""
 		self.host = host
 		self.port = port
 		self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
@@ -70,16 +112,27 @@ class NNTP:
 		self.file = self.sock.makefile('rb')
 		self.debugging = 0
 		self.welcome = self.getresp()
+		if readermode:
+			try:
+				self.welcome = self.shortcmd('mode reader')
+			except NNTPPermanentError:
+				# error 500, probably 'not implemented'
+				pass
 		if user:
 			resp = self.shortcmd('authinfo user '+user)
 			if resp[:3] == '381':
 				if not password:
-					raise error_reply, resp
+					raise NNTPReplyError(resp)
 				else:
 					resp = self.shortcmd(
 						'authinfo pass '+password)
 					if resp[:3] != '281':
-						raise error_perm, resp
+						raise NNTPPermanentError(resp)
+
+	# Get the welcome message from the server
+	# (this is read and squirreled away by __init__()).
+	# If the response code is 200, posting is allowed;
+	# if it 201, posting is not allowed
 
 	def getwelcome(self):
 		"""Get the welcome message from the server
@@ -128,11 +181,11 @@ class NNTP:
 		if self.debugging: print '*resp*', `resp`
 		c = resp[:1]
 		if c == '4':
-			raise error_temp, resp
+			raise NNTPTemporaryError(resp)
 		if c == '5':
-			raise error_perm, resp
+			raise NNTPPermanentError(resp)
 		if c not in '123':
-			raise error_proto, resp
+			raise NNTPProtocolError(resp)
 		return resp
 
 	def getlongresp(self):
@@ -140,7 +193,7 @@ class NNTP:
 		Raise various errors if the response indicates an error."""
 		resp = self.getresp()
 		if resp[:3] not in LONGRESP:
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		list = []
 		while 1:
 			line = self.getline()
@@ -206,7 +259,7 @@ class NNTP:
 
 		resp = self.shortcmd('GROUP ' + name)
 		if resp[:3] <> '211':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		words = string.split(resp)
 		count = first = last = 0
 		n = len(words)
@@ -230,7 +283,7 @@ class NNTP:
 	def statparse(self, resp):
 		"""Internal: parse the response of a STAT, NEXT or LAST command."""
 		if resp[:2] <> '22':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		words = string.split(resp)
 		nr = 0
 		id = ''
@@ -349,7 +402,7 @@ class NNTP:
 						    elem[6],
 						    elem[7]))
 			except IndexError:
-				raise error_data,line
+				raise NNTPDataError(line)
 		return resp,xover_lines
 
 	def xgtitle(self, group):
@@ -377,11 +430,11 @@ class NNTP:
 
 		resp = self.shortcmd("XPATH " + id)
 		if resp[:3] <> '223':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		try:
 			[resp_num, path] = string.split(resp)
 		except ValueError:
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		else:
 			return resp, path
 
@@ -395,14 +448,14 @@ class NNTP:
 
 		resp = self.shortcmd("DATE")
 		if resp[:3] <> '111':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		elem = string.split(resp)
 		if len(elem) != 2:
-			raise error_data, resp
+			raise NNTPDataError(resp)
 		date = elem[1][2:8]
 		time = elem[1][-6:]
 		if len(date) != 6 or len(time) != 6:
-			raise error_data, resp
+			raise NNTPDataError(resp)
 		return resp, date, time
 
 
@@ -415,7 +468,7 @@ class NNTP:
 		resp = self.shortcmd('POST')
 		# Raises error_??? if posting is not allowed
 		if resp[0] <> '3':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		while 1:
 			line = f.readline()
 			if not line:
@@ -439,7 +492,7 @@ class NNTP:
 		resp = self.shortcmd('IHAVE ' + id)
 		# Raises error_??? if the server already has it
 		if resp[0] <> '3':
-			raise error_reply, resp
+			raise NNTPReplyError(resp)
 		while 1:
 			line = f.readline()
 			if not line:
@@ -465,7 +518,7 @@ class NNTP:
 
 def _test():
 	"""Minimal test function."""
-	s = NNTP('news')
+	s = NNTP('news', readermode='reader')
 	resp, count, first, last, name = s.group('comp.lang.python')
 	print resp
 	print 'Group', name, 'has', count, 'articles, range', first, 'to', last