Index: example2366.py
===================================================================
--- example2366.py	(revision 0)
+++ example2366.py	(revision 0)
@@ -0,0 +1,22 @@
+class X(obj,obj2):
+  x = 3
+  __metaclass__ = Q
+  x = 7
+
+class X(obj):
+  x = 3
+  __metaclass__ = Q
+  x = 7
+
+class X():
+  x = 3
+  __metaclass__ = Q
+  x = 7
+
+
+class X():
+  __metaclass__=M
+
+
+
+# foo
Index: lib2to3/fixes/fix_metaclass.py
===================================================================
--- lib2to3/fixes/fix_metaclass.py	(revision 0)
+++ lib2to3/fixes/fix_metaclass.py	(revision 0)
@@ -0,0 +1,80 @@
+"""Fixer for __metaclass__ = X -> (metaclass=X) methods."""
+# Author: Jack Diederich
+
+# Local imports
+from .import basefix
+from .util import Name, syms, Node
+
+
+""" lib2to3 stuff that I couldn't grok
+    * it was tough to normalize the arglist in the class definition
+      so this has two or three code paths to handle the different cases
+    * I create arbitrary nodes to hold other nodes.  There is probably a
+      better way to do this.
+    * I clone nodes when I might not need to.
+    * BUG, if the final node (end of file) has the last char chopped off.
+      Name('passX') prints 'pass'
+"""
+
+class FixMetaclass(basefix.BaseFix):
+    PATTERN = """
+    classdef< 'class' any '(' (arglist<bases=any+>|bases=any*) ')' ':'
+              suite< any*
+                     meta_stmt=simple_stmt<
+                       expr_stmt< '__metaclass__' '=' meta_rhs=any+ > rest=any+
+                       > ender=any*
+                     >
+              >
+                
+    """
+    def transform(self, nodes, results):
+        bases = results['bases']
+
+        # class X(base1, base2, ...)
+        if len(bases) > 1:
+            old_parent = bases[0].parent
+            parent = old_parent.clone()
+            parent.children = []
+            new_bases = bases[:]
+        # class X() and class X(base)
+        else:
+            # create a placeholder before the ')'
+            parent = Node(259, []) # 259 is arbitrary, but it works
+            old_parent = Node(259, [])
+            new_bases = []
+                
+            for i, node in enumerate(nodes.children):
+                if node.type == 8: # RPAREN
+                    break
+            else:
+                raise Exception("Couldn't find right paren")
+            nodes.insert_child(i, old_parent)
+
+        if bases: # class X(obj)
+            new_bases.append(Name(','))
+            new_bases.append(Name(' '))
+        new_bases.append(Name('metaclass'))
+        new_bases.append(Name('='))
+
+        meta_rhs = results['meta_rhs']
+        meta_rhs[0].set_prefix('')
+        for ob in new_bases + meta_rhs:
+            ob_cp = ob.clone()
+            parent.append_child(ob_cp)
+
+        # put our new code where the old bases list was
+        old_parent.replace(parent)
+
+        # remove the old __metaclass__ line
+        meta_stmt = results['meta_stmt']
+        meta_stmt.remove()
+
+        # handle a class with just a __metaclass__ in the body
+        # (disabled because we can't garuantee that 'rest' is in the suite
+        rest = results['rest']
+        str_rest = ''.join(str(node) for node in rest).strip(' \t\n')
+        if False and not str_rest:
+            results['rest'][0].parent.append_child(Name('passX', prefix=''))
+
+
+        return # DONE!
Index: lib2to3/tests/test_fixers.py
===================================================================
--- lib2to3/tests/test_fixers.py	(revision 61654)
+++ lib2to3/tests/test_fixers.py	(working copy)
@@ -3122,7 +3122,43 @@
         a = "import .foo.bar as bang"
         self.check_both(b, a)
 
+class Test_metaclass(FixerTestCase):
+    fixer = 'metaclass'
 
+    def test_nometa(self):
+        self.unchanged('class X(): pass')
+        self.unchanged('class X(object): pass')
+        self.unchanged('class X(object1, object2): pass')
+
+    def test_onemeta(self):
+        old = 'class X(): __metaclass__ = Q\npass'
+        new = 'class X(metaclass=Q): pass'
+        self.check(old, new)
+        
+        old = 'class X(object): __metaclass__ = Q\npass'
+        new = 'class X(object, metaclass=Q): pass'
+        self.check(old, new)
+
+        old = '''
+class X(object):
+  __metaclass__ = Meta
+  bar = 7
+'''
+        new = '''
+class X(object, metaclass=Meta):
+  bar = 7
+'''
+        self.check(old, new)
+
+        old = '''
+class X(object):
+  bar = 7
+  __metaclass__ = Meta
+'''
+        self.check(old, new)
+
+
+
 if __name__ == "__main__":
     import __main__
     support.run_all_tests(__main__)