diff --git a/Tools/idle/AutoIndent.py b/Tools/idle/AutoIndent.py
index b1a2167..2913cc1 100644
--- a/Tools/idle/AutoIndent.py
+++ b/Tools/idle/AutoIndent.py
@@ -101,6 +101,10 @@
     indentwidth = 4
     tabwidth = TK_TABWIDTH_DEFAULT
 
+    # If context_use_ps1 is true, parsing searches back for a ps1 line;
+    # else searches back for closest preceding def or class.
+    context_use_ps1 = 0
+
     # When searching backwards for the closest preceding def or class,
     # first start num_context_lines[0] lines back, then
     # num_context_lines[1] lines back if that didn't work, and so on.
@@ -108,11 +112,10 @@
     # conceivable file).
     # Making the initial values larger slows things down more often.
     # OTOH, if you happen to find a line that looks like a def or class
-    # in a multiline string, and the start of the string isn't in the
-    # chunk, the parsing is utterly hosed.  Can't think of a way to
-    # stop that without always reparsing from the start of the file.
-    # doctest.py is a killer example of this (IDLE is useless for
-    # editing that!).
+    # in a multiline string, the parsing is utterly hosed.  Can't think
+    # of a way to stop that without always reparsing from the start
+    # of the file.  doctest.py is a killer example of this (IDLE is
+    # useless for editing that!).
     num_context_lines = 50, 500, 5000000
 
     def __init__(self, editwin):
@@ -126,6 +129,8 @@
                 self.indentwidth = value
             elif key == 'tabwidth':
                 self.tabwidth = value
+            elif key == 'context_use_ps1':
+                self.context_use_ps1 = value
             else:
                 raise KeyError, "bad option name: %s" % `key`
 
@@ -240,13 +245,17 @@
                 text.insert("insert linestart", '\n')
                 return "break"
             indent = line[:i]
-            # strip trailing whitespace
+            # strip whitespace before insert point
             i = 0
             while line and line[-1] in " \t":
                 line = line[:-1]
                 i = i+1
             if i:
                 text.delete("insert - %d chars" % i, "insert")
+            # strip whitespace after insert point
+            while text.get("insert") in " \t":
+                text.delete("insert")
+            # start new line
             text.insert("insert", '\n')
             # adjust indentation for continuations and block open/close
             lno = index2line(text.index('insert'))
@@ -255,7 +264,7 @@
                 startat = max(lno - context, 1)
                 rawtext = text.get(`startat` + ".0", "insert")
                 y.set_str(rawtext)
-                bod = y.find_last_def_or_class()
+                bod = y.find_last_def_or_class(self.context_use_ps1)
                 if bod is not None or startat == 1:
                     break
             y.set_lo(bod or 0)
diff --git a/Tools/idle/PyParse.py b/Tools/idle/PyParse.py
index e3b6e1f..ddafe39 100644
--- a/Tools/idle/PyParse.py
+++ b/Tools/idle/PyParse.py
@@ -7,10 +7,10 @@
 
 if 0:   # for throwaway debugging output
     def dump(*stuff):
-        import sys
         sys.__stdout__.write(string.join(map(str, stuff), " ") + "\n")
 
-# find a def or class stmt
+# Find a def or class stmt.
+
 _defclassre = re.compile(r"""
     ^
     [ \t]*
@@ -22,15 +22,17 @@
     )
 """, re.VERBOSE | re.MULTILINE).search
 
-# match blank line or non-indenting comment line
+# Match blank line or non-indenting comment line.
+
 _junkre = re.compile(r"""
     [ \t]*
-    (?: \# [^ \t\n] .* )?
+    (?: \# \S .* )?
     \n
 """, re.VERBOSE).match
 
-# match any flavor of string; the terminating quote is optional
-# so that we're robust in the face of incomplete program text
+# Match any flavor of string; the terminating quote is optional
+# so that we're robust in the face of incomplete program text.
+
 _match_stringre = re.compile(r"""
     \""" [^"\\]* (?:
                      (?: \\. | "(?!"") )
@@ -49,15 +51,16 @@
 |   ' [^'\\\n]* (?: \\. [^'\\\n]* )* '?
 """, re.VERBOSE | re.DOTALL).match
 
-# match a line that doesn't start with something interesting;
-# used to skip junk lines when searching for the first element
-# of a bracket structure
-_not_itemre = re.compile(r"""
+# Match a line that starts with something interesting;
+# used to find the first item of a bracket structure.
+
+_itemre = re.compile(r"""
     [ \t]*
-    [#\n\\]
+    [^\s#\\]    # if we match, m.end()-1 is the interesting char
 """, re.VERBOSE).match
 
-# match start of stmts that should be followed by a dedent
+# Match start of stmts that should be followed by a dedent.
+
 _closere = re.compile(r"""
     \s*
     (?: return
@@ -69,6 +72,17 @@
     \b
 """, re.VERBOSE).match
 
+# Chew up non-special chars as quickly as possible, but retaining
+# enough info to determine the last non-ws char seen; if match is
+# successful, and m.group(1) isn't None, m.end(1) less 1 is the
+# index of the last non-ws char matched.
+
+_chew_ordinaryre = re.compile(r"""
+    (?: \s+
+    |   ( [^\s[\](){}#'"\\]+ )
+    )+
+""", re.VERBOSE).match
+
 # Build translation table to map uninteresting chars to "x", open
 # brackets to "(", and close brackets to ")".
 
@@ -96,7 +110,7 @@
     # Return index of start of last (probable!) def or class stmt, or
     # None if none found.  It's only probable because we can't know
     # whether we're in a string without reparsing from the start of
-    # the file -- and that's too slow to bear.
+    # the file -- and that's too slow in large files for routine use.
     #
     # Ack, hack: in the shell window this kills us, because there's
     # no way to tell the differences between output, >>> etc and
@@ -104,22 +118,23 @@
     # look like it's in an unclosed paren!:
     # Python 1.5.2 (#0, Apr 13 1999, ...
 
-    def find_last_def_or_class(self, _defclassre=_defclassre):
+    def find_last_def_or_class(self, use_ps1, _defclassre=_defclassre):
         str, pos = self.str, None
-        i = 0
-        while 1:
-            m = _defclassre(str, i)
-            if m:
-                pos, i = m.span()
-            else:
-                break
-        if pos is None:
+        if use_ps1:
             # hack for shell window
             ps1 = '\n' + sys.ps1
             i = string.rfind(str, ps1)
             if i >= 0:
                 pos = i + len(ps1)
                 self.str = str[:pos-1] + '\n' + str[pos:]
+        else:
+            i = 0
+            while 1:
+                m = _defclassre(str, i)
+                if m:
+                    pos, i = m.span()
+                else:
+                    break
         return pos
 
     # Throw away the start of the string.  Intended to be called with
@@ -132,7 +147,7 @@
 
     # As quickly as humanly possible <wink>, find the line numbers (0-
     # based) of the non-continuation lines.
-    # Creates self.{stmts, continuation}.
+    # Creates self.{goodlines, continuation}.
 
     def _study1(self, _replace=string.replace, _find=string.find):
         if self.study_level >= 1:
@@ -158,80 +173,75 @@
         # whether & why the last stmt is a continuation.
         continuation = C_NONE
         level = lno = 0     # level is nesting level; lno is line number
-        self.stmts = stmts = [0]
-        push_stmt = stmts.append
+        self.goodlines = goodlines = [0]
+        push_good = goodlines.append
         i, n = 0, len(str)
         while i < n:
             ch = str[i]
-            # cases are checked in decreasing order of frequency
+            i = i+1
 
+            # cases are checked in decreasing order of frequency
             if ch == 'x':
-                i = i+1
                 continue
 
             if ch == '\n':
                 lno = lno + 1
                 if level == 0:
-                    push_stmt(lno)
+                    push_good(lno)
                     # else we're in an unclosed bracket structure
-                i = i+1
                 continue
 
             if ch == '(':
                 level = level + 1
-                i = i+1
                 continue
 
             if ch == ')':
                 if level:
                     level = level - 1
                     # else the program is invalid, but we can't complain
-                i = i+1
                 continue
 
             if ch == '"' or ch == "'":
                 # consume the string
                 quote = ch
-                if str[i:i+3] == quote * 3:
+                if str[i-1:i+2] == quote * 3:
                     quote = quote * 3
-                w = len(quote)
+                w = len(quote) - 1
                 i = i+w
                 while i < n:
                     ch = str[i]
+                    i = i+1
+
                     if ch == 'x':
-                        i = i+1
                         continue
 
-                    if str[i:i+w] == quote:
+                    if str[i-1:i+w] == quote:
                         i = i+w
                         break
 
                     if ch == '\n':
                         lno = lno + 1
-                        i = i+1
-                        if w == 1:
+                        if w == 0:
                             # unterminated single-quoted string
                             if level == 0:
-                                push_stmt(lno)
+                                push_good(lno)
                             break
                         continue
 
                     if ch == '\\':
-                        assert i+1 < n
-                        if str[i+1] == '\n':
+                        assert i < n
+                        if str[i] == '\n':
                             lno = lno + 1
-                        i = i+2
+                        i = i+1
                         continue
 
                     # else comment char or paren inside string
-                    i = i+1
 
                 else:
-                    # didn't break out of the loop, so it's an
-                    # unterminated triple-quoted string
-                    assert w == 3
+                    # didn't break out of the loop, so we're still
+                    # inside a string
                     continuation = C_STRING
-                continue
+                continue    # with outer loop
 
             if ch == '#':
                 # consume the comment
@@ -240,17 +250,12 @@
                 continue
 
             assert ch == '\\'
-            assert i+1 < n
-            if str[i+1] == '\n':
+            assert i < n
+            if str[i] == '\n':
                 lno = lno + 1
-                if i+2 == n:
+                if i+1 == n:
                     continuation = C_BACKSLASH
-            i = i+2
-
-        # Push the final line number as a sentinel value, regardless of
-        # whether it's continued.
-        if stmts[-1] != lno:
-            push_stmt(lno)
+            i = i+1
 
         # The last stmt may be continued for all 3 reasons.
         # String continuation takes precedence over bracket
@@ -259,6 +264,12 @@
             continuation = C_BRACKET
         self.continuation = continuation
 
+        # Push the final line number as a sentinel value, regardless of
+        # whether it's continued.
+        assert (continuation == C_NONE) == (goodlines[-1] == lno)
+        if goodlines[-1] != lno:
+            push_good(lno)
+
     def get_continuation_type(self):
         self._study1()
         return self.continuation
@@ -282,19 +293,16 @@
         self._study1()
         self.study_level = 2
 
-        self.lastch = ""
-
         # Set p and q to slice indices of last interesting stmt.
-        str, stmts = self.str, self.stmts
-        i = len(stmts) - 1
+        str, goodlines = self.str, self.goodlines
+        i = len(goodlines) - 1
         p = len(str)    # index of newest line
-        found = 0
         while i:
             assert p
-            # p is the index of the stmt at line number stmts[i].
-            # Move p back to the stmt at line number stmts[i-1].
+            # p is the index of the stmt at line number goodlines[i].
+            # Move p back to the stmt at line number goodlines[i-1].
             q = p
-            for nothing in range(stmts[i-1], stmts[i]):
+            for nothing in range(goodlines[i-1], goodlines[i]):
                 # tricky: sets p to 0 if no preceding newline
                 p = _rfind(str, '\n', 0, p-1) + 1
             # The stmt str[p:q] isn't a continuation, but may be blank
@@ -302,16 +310,44 @@
             if  _junkre(str, p):
                 i = i-1
             else:
-                found = 1
                 break
+        if i == 0:
+            # nothing but junk!
+            assert p == 0
+            q = p
         self.stmt_start, self.stmt_end = p, q
 
         # Analyze this stmt, to find the last open bracket (if any)
         # and last interesting character (if any).
+        lastch = ""
         stack = []  # stack of open bracket indices
         push_stack = stack.append
         while p < q:
+            # suck up all except ()[]{}'"#\\
+            m = _chew_ordinaryre(str, p, q)
+            if m:
+                i = m.end(1) - 1    # last non-ws (if any)
+                if i >= 0:
+                    lastch = str[i]
+                p = m.end()
+                if p >= q:
+                    break
+
             ch = str[p]
+
+            if ch in "([{":
+                push_stack(p)
+                lastch = ch
+                p = p+1
+                continue
+
+            if ch in ")]}":
+                if stack:
+                    del stack[-1]
+                lastch = ch
+                p = p+1
+                continue
+
             if ch == '"' or ch == "'":
                 # consume string
                 # Note that study1 did this with a Python loop, but
@@ -320,7 +356,7 @@
                 # strings to a couple of characters per line.  study1
                 # also needed to keep track of newlines, and we don't
                 # have to.
-                self.lastch = ch
+                lastch = ch
                 p = _match_stringre(str, p, q).end()
                 continue
 
@@ -330,24 +366,17 @@
                 assert p > 0
                 continue
 
-            if ch == '\\':
-                assert p+1 < q
-                if str[p+1] != '\n':
-                    # the program is invalid, but can't complain
-                    self.lastch = str[p:p+2]
-                p = p+2
-                continue
-
-            if ch not in _ws:
-                self.lastch = ch
-                if ch in "([{":
-                    push_stack(p)
-                elif ch in ")]}" and stack:
-                    del stack[-1]
-            p = p+1
+            assert ch == '\\'
+            p = p+1     # beyond backslash
+            assert p < q
+            if str[p] != '\n':
+                # the program is invalid, but can't complain
+                lastch = ch + str[p]
+            p = p+1     # beyond escaped char
 
         # end while p < q:
 
+        self.lastch = lastch
         if stack:
             self.lastopenbracketpos = stack[-1]
 
@@ -361,25 +390,24 @@
         str = self.str
         n = len(str)
         origi = i = string.rfind(str, '\n', 0, j) + 1
-        j = j+1
-        # find first list item
-        while _not_itemre(str, j):
-            # this line is junk; advance to the next line
-            i = _find(str, '\n', j)
-            if i < 0:
+        j = j+1     # one beyond open bracket
+        # find first list item; set i to start of its line
+        while j < n:
+            m = _itemre(str, j)
+            if m:
+                j = m.end() - 1     # index of first interesting char
+                extra = 0
                 break
-            j = i = i+1
-        if i < 0 or j >= n:
+            else:
+                # this line is junk; advance to next line
+                i = j = _find(str, '\n', j) + 1
+        else:
             # nothing interesting follows the bracket;
             # reproduce the bracket line's indentation + a level
             j = i = origi
+            while str[j] in " \t":
+                j = j+1
             extra = self.indentwidth
-        else:
-            # the first list item begins on this line; line up with
-            # the first interesting character
-            extra = 0
-        while str[j] in " \t":
-            j = j+1
         return len(string.expandtabs(str[i:j],
                                      self.tabwidth)) + extra
 
@@ -389,8 +417,8 @@
 
     def get_num_lines_in_stmt(self):
         self._study1()
-        stmts = self.stmts
-        return stmts[-1] - stmts[-2]
+        goodlines = self.goodlines
+        return goodlines[-1] - goodlines[-2]
 
     # Assuming continuation is C_BACKSLASH, return the number of spaces
     # the next line should be indented.  Also assuming the new line is
@@ -404,6 +432,9 @@
         while str[i] in " \t":
             i = i+1
         startpos = i
+
+        # See whether the initial line starts an assignment stmt; i.e.,
+        # look for an = operator
         endpos = string.find(str, '\n', startpos) + 1
         found = level = 0
         while i < endpos:
@@ -420,8 +451,8 @@
             elif ch == '#':
                 break
             elif level == 0 and ch == '=' and \
-                 (i == 0 or str[i-1] not in "=<>!") and \
-                 str[i+1] != '=':
+                   (i == 0 or str[i-1] not in "=<>!") and \
+                   str[i+1] != '=':
                 found = 1
                 break
             else:
@@ -450,7 +481,6 @@
     def get_base_indent_string(self):
         self._study2()
         i, n = self.stmt_start, self.stmt_end
-        assert i is not None
         j = i
         str = self.str
         while j < n and str[j] in " \t":
diff --git a/Tools/idle/PyShell.py b/Tools/idle/PyShell.py
index bd095cf..a618ad1 100644
--- a/Tools/idle/PyShell.py
+++ b/Tools/idle/PyShell.py
@@ -291,7 +291,7 @@
         __builtin__.quit = __builtin__.exit = "To exit, type Ctrl-D."
 
         self.auto = self.extensions["AutoIndent"] # Required extension
-        self.auto.config(usetabs=1, indentwidth=8)
+        self.auto.config(usetabs=1, indentwidth=8, context_use_ps1=1)
 
         text = self.text
         text.configure(wrap="char")