diff --git a/Lib/antigravity.py b/Lib/antigravity.py
new file mode 100644
index 0000000..7fb7d82
--- /dev/null
+++ b/Lib/antigravity.py
@@ -0,0 +1,4 @@
+
+import webbrowser
+
+webbrowser.open("http://xkcd.com/353/")
diff --git a/Lib/idlelib/PyShell.py b/Lib/idlelib/PyShell.py
index a7fd928..cca91ad 100644
--- a/Lib/idlelib/PyShell.py
+++ b/Lib/idlelib/PyShell.py
@@ -52,18 +52,22 @@
 except ImportError:
     pass
 else:
-    def idle_showwarning(message, category, filename, lineno):
+    def idle_showwarning(message, category, filename, lineno,
+                         file=None, line=None):
         file = warning_stream
         try:
-            file.write(warnings.formatwarning(message, category, filename, lineno))
+            file.write(warnings.formatwarning(message, category, filename,\
+                                              lineno, file=file, line=line))
         except IOError:
             pass  ## file (probably __stderr__) is invalid, warning dropped.
     warnings.showwarning = idle_showwarning
-    def idle_formatwarning(message, category, filename, lineno):
+    def idle_formatwarning(message, category, filename, lineno,
+                           file=None, line=None):
         """Format warnings the IDLE way"""
         s = "\nWarning (from warnings module):\n"
         s += '  File \"%s\", line %s\n' % (filename, lineno)
-        line = linecache.getline(filename, lineno).strip()
+        line = linecache.getline(filename, lineno).strip() \
+            if line is None else line
         if line:
             s += "    %s\n" % line
         s += "%s: %s\n>>> " % (category.__name__, message)
diff --git a/Lib/idlelib/run.py b/Lib/idlelib/run.py
index 62dc316..806456a 100644
--- a/Lib/idlelib/run.py
+++ b/Lib/idlelib/run.py
@@ -24,11 +24,13 @@
 except ImportError:
     pass
 else:
-    def idle_formatwarning_subproc(message, category, filename, lineno):
+    def idle_formatwarning_subproc(message, category, filename, lineno,
+                                   file=None, line=None):
         """Format warnings the IDLE way"""
         s = "\nWarning (from warnings module):\n"
         s += '  File \"%s\", line %s\n' % (filename, lineno)
-        line = linecache.getline(filename, lineno).strip()
+        line = linecache.getline(filename, lineno).strip() \
+            if line is None else line
         if line:
             s += "    %s\n" % line
         s += "%s: %s\n" % (category.__name__, message)
diff --git a/Lib/lib2to3/fixes/fix_next.py b/Lib/lib2to3/fixes/fix_next.py
index 9791333..9f1861e 100644
--- a/Lib/lib2to3/fixes/fix_next.py
+++ b/Lib/lib2to3/fixes/fix_next.py
@@ -28,15 +28,19 @@
                      any* > >
     |
     global=global_stmt< 'global' any* 'next' any* >
-    |
-    mod=file_input< any+ >
     """
 
     order = "pre" # Pre-order tree traversal
 
     def start_tree(self, tree, filename):
         super(FixNext, self).start_tree(tree, filename)
-        self.shadowed_next = False
+
+        n = find_binding('next', tree)
+        if n:
+            self.warning(n, bind_warning)
+            self.shadowed_next = True
+        else:
+            self.shadowed_next = False
 
     def transform(self, node, results):
         assert results
@@ -69,11 +73,6 @@
         elif "global" in results:
             self.warning(node, bind_warning)
             self.shadowed_next = True
-        elif mod:
-            n = find_binding('next', mod)
-            if n:
-                self.warning(n, bind_warning)
-                self.shadowed_next = True
 
 
 ### The following functions help test if node is part of an assignment
diff --git a/Lib/lib2to3/fixes/fix_set_literal.py b/Lib/lib2to3/fixes/fix_set_literal.py
new file mode 100644
index 0000000..414b1df
--- /dev/null
+++ b/Lib/lib2to3/fixes/fix_set_literal.py
@@ -0,0 +1,52 @@
+"""
+Optional fixer to transform set() calls to set literals.
+"""
+
+# Author: Benjamin Peterson
+
+from lib2to3 import fixer_base, pytree
+from lib2to3.fixer_util import token, syms
+
+
+
+class FixSetLiteral(fixer_base.BaseFix):
+
+    explicit = True
+
+    PATTERN = """power< 'set' trailer< '('
+                     (atom=atom< '[' (items=listmaker< any ((',' any)* [',']) >
+                                |
+                                single=any) ']' >
+                     |
+                     atom< '(' items=testlist_gexp< any ((',' any)* [',']) > ')' >
+                     )
+                     ')' > >
+              """
+
+    def transform(self, node, results):
+        single = results.get("single")
+        if single:
+            # Make a fake listmaker
+            fake = pytree.Node(syms.listmaker, [single.clone()])
+            single.replace(fake)
+            items = fake
+        else:
+            items = results["items"]
+
+        # Build the contents of the literal
+        literal = [pytree.Leaf(token.LBRACE, "{")]
+        literal.extend(n.clone() for n in items.children)
+        literal.append(pytree.Leaf(token.RBRACE, "}"))
+        # Set the prefix of the right brace to that of the ')' or ']'
+        literal[-1].set_prefix(items.get_next_sibling().get_prefix())
+        maker = pytree.Node(syms.dictsetmaker, literal)
+        maker.set_prefix(node.get_prefix())
+
+        # If the original was a one tuple, we need to remove the extra comma.
+        if len(maker.children) == 4:
+            n = maker.children[2]
+            n.remove()
+            maker.children[-1].set_prefix(n.get_prefix())
+
+        # Finally, replace the set call with our shiny new literal.
+        return maker
diff --git a/Lib/lib2to3/main.py b/Lib/lib2to3/main.py
index b286de8..4cb0362 100644
--- a/Lib/lib2to3/main.py
+++ b/Lib/lib2to3/main.py
@@ -15,10 +15,31 @@
     Prints output to stdout.
     """
 
+    def __init__(self, fixers, options, explicit, nobackups):
+        self.nobackups = nobackups
+        super(StdoutRefactoringTool, self).__init__(fixers, options, explicit)
+
     def log_error(self, msg, *args, **kwargs):
         self.errors.append((msg, args, kwargs))
         self.logger.error(msg, *args, **kwargs)
 
+    def write_file(self, new_text, filename, old_text):
+        if not self.nobackups:
+            # Make backup
+            backup = filename + ".bak"
+            if os.path.lexists(backup):
+                try:
+                    os.remove(backup)
+                except os.error as err:
+                    self.log_message("Can't remove backup %s", backup)
+            try:
+                os.rename(filename, backup)
+            except os.error as err:
+                self.log_message("Can't rename %s to %s", filename, backup)
+        # Actually write the new file
+        super(StdoutRefactoringTool, self).write_file(new_text,
+                                                      filename, old_text)
+
     def print_output(self, lines):
         for line in lines:
             print(line)
@@ -39,7 +60,9 @@
     parser.add_option("-d", "--doctests_only", action="store_true",
                       help="Fix up doctests only")
     parser.add_option("-f", "--fix", action="append", default=[],
-                      help="Each FIX specifies a transformation; default all")
+                      help="Each FIX specifies a transformation; default: all")
+    parser.add_option("-x", "--nofix", action="append", default=[],
+                      help="Prevent a fixer from being run.")
     parser.add_option("-l", "--list-fixes", action="store_true",
                       help="List available transformations (fixes/fix_*.py)")
     parser.add_option("-p", "--print-function", action="store_true",
@@ -48,10 +71,14 @@
                       help="More verbose logging")
     parser.add_option("-w", "--write", action="store_true",
                       help="Write back modified files")
+    parser.add_option("-n", "--nobackups", action="store_true", default=False,
+                      help="Don't write backups for modified files.")
 
     # Parse command line arguments
     refactor_stdin = False
     options, args = parser.parse_args(args)
+    if not options.write and options.nobackups:
+        parser.error("Can't use -n without -w")
     if options.list_fixes:
         print("Available transformations for the -f/--fix option:")
         for fixname in refactor.get_all_fix_names(fixer_pkg):
@@ -74,15 +101,22 @@
 
     # Initialize the refactoring tool
     rt_opts = {"print_function" : options.print_function}
-    avail_names = refactor.get_fixers_from_package(fixer_pkg)
-    explicit = []
+    avail_fixes = set(refactor.get_fixers_from_package(fixer_pkg))
+    unwanted_fixes = set(fixer_pkg + ".fix_" + fix for fix in options.nofix)
+    explicit = set()
     if options.fix:
-        explicit = [fixer_pkg + ".fix_" + fix
-                    for fix in options.fix if fix != "all"]
-        fixer_names = avail_names if "all" in options.fix else explicit
+        all_present = False
+        for fix in options.fix:
+            if fix == "all":
+                all_present = True
+            else:
+                explicit.add(fixer_pkg + ".fix_" + fix)
+        requested = avail_fixes.union(explicit) if all_present else explicit
     else:
-        fixer_names = avail_names
-    rt = StdoutRefactoringTool(fixer_names, rt_opts, explicit=explicit)
+        requested = avail_fixes.union(explicit)
+    fixer_names = requested.difference(unwanted_fixes)
+    rt = StdoutRefactoringTool(sorted(fixer_names), rt_opts, sorted(explicit),
+                               options.nobackups)
 
     # Refactor all files and directories passed as arguments
     if not rt.errors:
diff --git a/Lib/lib2to3/refactor.py b/Lib/lib2to3/refactor.py
index 82a2d45..31c80be 100755
--- a/Lib/lib2to3/refactor.py
+++ b/Lib/lib2to3/refactor.py
@@ -36,9 +36,7 @@
     pkg = __import__(fixer_pkg, [], [], ["*"])
     fixer_dir = os.path.dirname(pkg.__file__)
     fix_names = []
-    names = os.listdir(fixer_dir)
-    names.sort()
-    for name in names:
+    for name in sorted(os.listdir(fixer_dir)):
         if name.startswith("fix_") and name.endswith(".py"):
             if remove_prefix:
                 name = name[4:]
@@ -253,7 +251,7 @@
             there were errors during the parse.
         """
         try:
-            tree = self.driver.parse_string(data,1)
+            tree = self.driver.parse_string(data)
         except Exception as err:
             self.log_error("Can't parse %s: %s: %s",
                            name, err.__class__.__name__, err)
@@ -352,23 +350,13 @@
         else:
             self.log_debug("Not writing changes to %s", filename)
 
-    def write_file(self, new_text, filename, old_text=None):
+    def write_file(self, new_text, filename, old_text):
         """Writes a string to a file.
 
         It first shows a unified diff between the old text and the new text, and
         then rewrites the file; the latter is only done if the write option is
         set.
         """
-        backup = filename + ".bak"
-        if os.path.lexists(backup):
-            try:
-                os.remove(backup)
-            except os.error as err:
-                self.log_message("Can't remove backup %s", backup)
-        try:
-            os.rename(filename, backup)
-        except os.error as err:
-            self.log_message("Can't rename %s to %s", filename, backup)
         try:
             f = open(filename, "w")
         except os.error as err:
diff --git a/Lib/lib2to3/tests/data/README b/Lib/lib2to3/tests/data/README
index c48c608..7aa47e4 100644
--- a/Lib/lib2to3/tests/data/README
+++ b/Lib/lib2to3/tests/data/README
@@ -1,5 +1,6 @@
-Files in this directory:
+In this directory:
 - py2_test_grammar.py -- test file that exercises most/all of Python 2.x's grammar.
 - py3_test_grammar.py -- test file that exercises most/all of Python 3.x's grammar.
 - infinite_recursion.py -- test file that causes lib2to3's faster recursive pattern matching
   scheme to fail, but passes when lib2to3 falls back to iterative pattern matching.
+- fixes/ -- for use by test_refactor.py
diff --git a/Lib/lib2to3/tests/test_fixers.py b/Lib/lib2to3/tests/test_fixers.py
index b4ca5cd..83c1ba5 100755
--- a/Lib/lib2to3/tests/test_fixers.py
+++ b/Lib/lib2to3/tests/test_fixers.py
@@ -3385,6 +3385,134 @@
         """
         self.check_both(b, a)
 
+
+class Test_set_literal(FixerTestCase):
+
+    fixer = "set_literal"
+
+    def test_basic(self):
+        b = """set([1, 2, 3])"""
+        a = """{1, 2, 3}"""
+        self.check(b, a)
+
+        b = """set((1, 2, 3))"""
+        a = """{1, 2, 3}"""
+        self.check(b, a)
+
+        b = """set((1,))"""
+        a = """{1}"""
+        self.check(b, a)
+
+        b = """set([1])"""
+        self.check(b, a)
+
+        b = """set((a, b))"""
+        a = """{a, b}"""
+        self.check(b, a)
+
+        b = """set([a, b])"""
+        self.check(b, a)
+
+        b = """set((a*234, f(args=23)))"""
+        a = """{a*234, f(args=23)}"""
+        self.check(b, a)
+
+        b = """set([a*23, f(23)])"""
+        a = """{a*23, f(23)}"""
+        self.check(b, a)
+
+        b = """set([a-234**23])"""
+        a = """{a-234**23}"""
+        self.check(b, a)
+
+    def test_listcomps(self):
+        b = """set([x for x in y])"""
+        a = """{x for x in y}"""
+        self.check(b, a)
+
+        b = """set([x for x in y if x == m])"""
+        a = """{x for x in y if x == m}"""
+        self.check(b, a)
+
+        b = """set([x for x in y for a in b])"""
+        a = """{x for x in y for a in b}"""
+        self.check(b, a)
+
+        b = """set([f(x) - 23 for x in y])"""
+        a = """{f(x) - 23 for x in y}"""
+        self.check(b, a)
+
+    def test_whitespace(self):
+        b = """set( [1, 2])"""
+        a = """{1, 2}"""
+        self.check(b, a)
+
+        b = """set([1 ,  2])"""
+        a = """{1 ,  2}"""
+        self.check(b, a)
+
+        b = """set([ 1 ])"""
+        a = """{ 1 }"""
+        self.check(b, a)
+
+        b = """set( [1] )"""
+        a = """{1}"""
+        self.check(b, a)
+
+        b = """set([  1,  2  ])"""
+        a = """{  1,  2  }"""
+        self.check(b, a)
+
+        b = """set([x  for x in y ])"""
+        a = """{x  for x in y }"""
+        self.check(b, a)
+
+        b = """set(
+                   [1, 2]
+               )
+            """
+        a = """{1, 2}\n"""
+        self.check(b, a)
+
+    def test_comments(self):
+        b = """set((1, 2)) # Hi"""
+        a = """{1, 2} # Hi"""
+        self.check(b, a)
+
+        # This isn't optimal behavior, but the fixer is optional.
+        b = """
+            # Foo
+            set( # Bar
+               (1, 2)
+            )
+            """
+        a = """
+            # Foo
+            {1, 2}
+            """
+        self.check(b, a)
+
+    def test_unchanged(self):
+        s = """set()"""
+        self.unchanged(s)
+
+        s = """set(a)"""
+        self.unchanged(s)
+
+        s = """set(a, b, c)"""
+        self.unchanged(s)
+
+        # Don't transform generators because they might have to be lazy.
+        s = """set(x for x in y)"""
+        self.unchanged(s)
+
+        s = """set(x for x in y if z)"""
+        self.unchanged(s)
+
+        s = """set(a*823-23**2 + f(23))"""
+        self.unchanged(s)
+
+
 class Test_sys_exc(FixerTestCase):
     fixer = "sys_exc"
 
diff --git a/Lib/lib2to3/tests/test_pytree.py b/Lib/lib2to3/tests/test_pytree.py
index 57c8a82..61c592a 100755
--- a/Lib/lib2to3/tests/test_pytree.py
+++ b/Lib/lib2to3/tests/test_pytree.py
@@ -353,29 +353,29 @@
         # Build a pattern matching a leaf
         pl = pytree.LeafPattern(100, "foo", name="pl")
         r = {}
-        self.assertEqual(pl.match(root, results=r), False)
+        self.assertFalse(pl.match(root, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pl.match(n1, results=r), False)
+        self.assertFalse(pl.match(n1, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pl.match(n2, results=r), False)
+        self.assertFalse(pl.match(n2, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pl.match(l1, results=r), True)
+        self.assertTrue(pl.match(l1, results=r))
         self.assertEqual(r, {"pl": l1})
         r = {}
-        self.assertEqual(pl.match(l2, results=r), False)
+        self.assertFalse(pl.match(l2, results=r))
         self.assertEqual(r, {})
         # Build a pattern matching a node
         pn = pytree.NodePattern(1000, [pl], name="pn")
-        self.assertEqual(pn.match(root, results=r), False)
+        self.assertFalse(pn.match(root, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pn.match(n1, results=r), False)
+        self.assertFalse(pn.match(n1, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pn.match(n2, results=r), True)
+        self.assertTrue(pn.match(n2, results=r))
         self.assertEqual(r, {"pn": n2, "pl": l3})
         r = {}
-        self.assertEqual(pn.match(l1, results=r), False)
+        self.assertFalse(pn.match(l1, results=r))
         self.assertEqual(r, {})
-        self.assertEqual(pn.match(l2, results=r), False)
+        self.assertFalse(pn.match(l2, results=r))
         self.assertEqual(r, {})
 
     def testWildcardPatterns(self):
@@ -391,11 +391,11 @@
         pn = pytree.NodePattern(1000, [pl], name="pn")
         pw = pytree.WildcardPattern([[pn], [pl, pl]], name="pw")
         r = {}
-        self.assertEqual(pw.match_seq([root], r), False)
+        self.assertFalse(pw.match_seq([root], r))
         self.assertEqual(r, {})
-        self.assertEqual(pw.match_seq([n1], r), False)
+        self.assertFalse(pw.match_seq([n1], r))
         self.assertEqual(r, {})
-        self.assertEqual(pw.match_seq([n2], r), True)
+        self.assertTrue(pw.match_seq([n2], r))
         # These are easier to debug
         self.assertEqual(sorted(r.keys()), ["pl", "pn", "pw"])
         self.assertEqual(r["pl"], l1)
@@ -404,7 +404,7 @@
         # But this is equivalent
         self.assertEqual(r, {"pl": l1, "pn": n2, "pw": [n2]})
         r = {}
-        self.assertEqual(pw.match_seq([l1, l3], r), True)
+        self.assertTrue(pw.match_seq([l1, l3], r))
         self.assertEqual(r, {"pl": l3, "pw": [l1, l3]})
         self.assert_(r["pl"] is l3)
         r = {}
diff --git a/Lib/lib2to3/tests/test_refactor.py b/Lib/lib2to3/tests/test_refactor.py
index 0717479..0814ad7 100644
--- a/Lib/lib2to3/tests/test_refactor.py
+++ b/Lib/lib2to3/tests/test_refactor.py
@@ -123,7 +123,6 @@
 
     def test_refactor_file(self):
         test_file = os.path.join(FIXER_DIR, "parrot_example.py")
-        backup = test_file + ".bak"
         old_contents = open(test_file, "r").read()
         rt = self.rt()
 
@@ -133,14 +132,8 @@
         rt.refactor_file(test_file, True)
         try:
             self.assertNotEqual(old_contents, open(test_file, "r").read())
-            self.assertTrue(os.path.exists(backup))
-            self.assertEqual(old_contents, open(backup, "r").read())
         finally:
             open(test_file, "w").write(old_contents)
-            try:
-                os.unlink(backup)
-            except OSError:
-                pass
 
     def test_refactor_docstring(self):
         rt = self.rt()