Index: Lib/re.py
===================================================================
--- Lib/re.py	(revision 62564)
+++ Lib/re.py	(working copy)
@@ -196,22 +196,15 @@
     "Compile a template pattern, returning a pattern object"
     return _compile(pattern, flags|T)
 
-_alphanum = {}
-for c in 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890':
-    _alphanum[c] = 1
-del c
+_special = frozenset(r'.^$*+?{}[]\|()')
 
 def escape(pattern):
-    "Escape all non-alphanumeric characters in pattern."
+    "Escape all special characters in pattern."
     s = list(pattern)
-    alphanum = _alphanum
-    for i in range(len(pattern)):
-        c = pattern[i]
-        if c not in alphanum:
-            if c == "\000":
-                s[i] = "\\000"
-            else:
-                s[i] = "\\" + c
+    special = _special
+    for i, c in enumerate(pattern):
+        if c in special:
+            s[i] = "\\" + c
     return pattern[:0].join(s)
 
 # --------------------------------------------------------------------
Index: Lib/test/test_re.py
===================================================================
--- Lib/test/test_re.py	(revision 62564)
+++ Lib/test/test_re.py	(working copy)
@@ -442,6 +442,12 @@
         self.assertEqual(pat.match(p) is not None, True)
         self.assertEqual(pat.match(p).span(), (0,256))
 
+        # letters, digits, and _ should be left alone
+        same = "abcdefghijklmnopqrstuvwxyz" + \
+               "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + \
+               "0123456789_"
+        self.assertEqual(re.escape(same), same)
+
     def test_pickling(self):
         import pickle
         self.pickle_test(pickle)