Index: Lib/urllib.py
===================================================================
--- Lib/urllib.py	(revision 81076)
+++ Lib/urllib.py	(working copy)
@@ -1162,8 +1162,11 @@
 def unquote(s):
     """unquote('abc%20def') -> 'abc def'."""
     res = s.split('%')
-    for i in xrange(1, len(res)):
-        item = res[i]
+    if len(res) == 1:
+        return s
+    i = 0
+    for item in res[1:]:
+        i += 1
         try:
             res[i] = _hextochr[item[:2]] + item[2:]
         except KeyError:
@@ -1177,12 +1180,19 @@
     s = s.replace('+', ' ')
     return unquote(s)
 
-always_safe = ('ABCDEFGHIJKLMNOPQRSTUVWXYZ'
-               'abcdefghijklmnopqrstuvwxyz'
-               '0123456789' '_.-')
+always_safe = frozenset('ABCDEFGHIJKLMNOPQRSTUVWXYZ'
+                        'abcdefghijklmnopqrstuvwxyz'
+                        '0123456789' '_.-')
+_safe_map = dict((c, c) for c in always_safe)
+for i in xrange(0x80):
+    c = chr(i)
+    if c not in _safe_map:
+        _safe_map[c] = '%%%02X' % i
+_safe_map.update((chr(i), '%%%02X' % i) for i in xrange(0x80, 0x100))
 _safemaps = {}
 
-def quote(s, safe = '/'):
+
+def quote(s, safe='/'):
     """quote('abc def') -> 'abc%20def'
 
     Each part of a URL, e.g. the path info, the query, etc., has a
@@ -1203,27 +1213,30 @@
     called on a path where the existing slash characters are used as
     reserved characters.
     """
+    if not s:
+        return s
     cachekey = (safe, always_safe)
     try:
-        safe_map = _safemaps[cachekey]
+        (strans, safe_get) = _safemaps[cachekey]
     except KeyError:
-        safe += always_safe
-        safe_map = {}
-        for i in range(256):
-            c = chr(i)
-            safe_map[c] = (c in safe) and c or ('%%%02X' % i)
-        _safemaps[cachekey] = safe_map
-    res = map(safe_map.__getitem__, s)
-    return ''.join(res)
+        safe_set = always_safe | set(safe)
+        strans = ''.join('% '[chr(i) in safe_set] for i in xrange(0x100))
+        safe_map = _safe_map.copy()
+        safe_map.update((c, c) for c in safe)
+        safe_get = safe_map.__getitem__
+        _safemaps[cachekey] = (strans, safe_get)
+    if '%' not in s.translate(strans):
+        return s
+    return ''.join(map(safe_get, s))
 
-def quote_plus(s, safe = ''):
+def quote_plus(s, safe=''):
     """Quote the query fragment of a URL; replacing ' ' with '+'"""
     if ' ' in s:
         s = quote(s, safe + ' ')
         return s.replace(' ', '+')
     return quote(s, safe)
 
-def urlencode(query,doseq=0):
+def urlencode(query, doseq=0):
     """Encode a sequence of two-element tuples or dictionary into a URL query string.
 
     If any values in the query arg are sequences and doseq is true, each