diff -r e539761d45e3 -r 704d1bcc942e Include/code.h
--- a/Include/code.h	Thu Nov 14 15:35:47 2013 +0100
+++ b/Include/code.h	Mon Nov 25 12:51:33 2013 +0100
@@ -30,6 +30,8 @@ typedef struct {
 				   Objects/lnotab_notes.txt for details. */
     void *co_zombieframe;     /* for optimization only (see frameobject.c) */
     PyObject *co_weakreflist;   /* to support weakrefs to code objects */
+    PyObject *co_annotation;   /* Annotation function (used for formatting
+                                  additional info in traceback) */
 } PyCodeObject;
 
 /* Masks for co_flags above */
diff -r e539761d45e3 -r 704d1bcc942e Lib/traceback.py
--- a/Lib/traceback.py	Thu Nov 14 15:35:47 2013 +0100
+++ b/Lib/traceback.py	Mon Nov 25 12:51:33 2013 +0100
@@ -15,8 +15,11 @@ import operator
 #
 
 def _format_list_iter(extracted_list):
-    for filename, lineno, name, line in extracted_list:
-        item = '  File "{}", line {}, in {}\n'.format(filename, lineno, name)
+    for filename, lineno, name, line, annotation, frame in extracted_list:
+        item = '  File "{}", line {}, in {}'.format(filename, lineno, name)
+        if annotation is not None:
+            item += ': {}'.format(annotation(frame))
+        item += '\n'
         if line:
             item = item + '    {}\n'.format(line.strip())
         yield item
@@ -60,6 +63,7 @@ def _extract_tb_or_stack_iter(curr, limi
         co = f.f_code
         filename = co.co_filename
         name = co.co_name
+        annotation = co.co_annotation
 
         linecache.checkcache(filename)
         line = linecache.getline(filename, lineno, f.f_globals)
@@ -69,7 +73,7 @@ def _extract_tb_or_stack_iter(curr, limi
         else:
             line = None
 
-        yield (filename, lineno, name, line)
+        yield (filename, lineno, name, line, annotation, f)
         curr = next_item
         n += 1
 
@@ -310,3 +314,11 @@ def clear_frames(tb):
             # Ignore the exception raised if the frame is still executing.
             pass
         tb = tb.tb_next
+
+def annotate(format):
+    def wrapper(f):
+        def formatter(frame):
+            return format.format(**frame.f_locals)
+        f.__code__.co_annotation = formatter
+        return f
+    return wrapper
diff -r e539761d45e3 -r 704d1bcc942e Objects/codeobject.c
--- a/Objects/codeobject.c	Thu Nov 14 15:35:47 2013 +0100
+++ b/Objects/codeobject.c	Mon Nov 25 12:51:33 2013 +0100
@@ -152,6 +152,7 @@ PyCode_New(int argcount, int kwonlyargco
     co->co_lnotab = lnotab;
     co->co_zombieframe = NULL;
     co->co_weakreflist = NULL;
+    co->co_annotation = NULL;
     return co;
 }
 
@@ -221,6 +222,7 @@ static PyMemberDef code_memberlist[] = {
     {"co_name",         T_OBJECT,       OFF(co_name),           READONLY},
     {"co_firstlineno", T_INT,           OFF(co_firstlineno),    READONLY},
     {"co_lnotab",       T_OBJECT,       OFF(co_lnotab),         READONLY},
+    {"co_annotation",   T_OBJECT,       OFF(co_annotation),     0},
     {NULL}      /* Sentinel */
 };
 
diff -r e539761d45e3 -r 704d1bcc942e Python/traceback.c
--- a/Python/traceback.c	Thu Nov 14 15:35:47 2013 +0100
+++ b/Python/traceback.c	Mon Nov 25 12:51:33 2013 +0100
@@ -343,15 +343,38 @@ int
 }
 
 static int
-tb_displayline(PyObject *f, PyObject *filename, int lineno, PyObject *name)
+tb_displayline(PyObject *f, PyTracebackObject *tb)
 {
     int err;
     PyObject *line;
 
+    PyObject *filename = tb->tb_frame->f_code->co_filename;
+    int lineno = tb->tb_lineno;
+    PyObject *name = tb->tb_frame->f_code->co_name;
+    PyObject *annotation = tb->tb_frame->f_code->co_annotation;
+
     if (filename == NULL || name == NULL)
         return -1;
-    line = PyUnicode_FromFormat("  File \"%U\", line %d, in %U\n",
-                                filename, lineno, name);
+    if (annotation == NULL)
+        line = PyUnicode_FromFormat("  File \"%U\", line %d, in %U\n",
+                                    filename, lineno, name);
+    else
+    {
+        PyObject *formatted = PyObject_CallFunctionObjArgs(annotation,
+                                                           tb->tb_frame, NULL);
+        if (formatted == NULL)
+        {
+            /* If formatting the annotation failed, retry without the annotation */
+            line = PyUnicode_FromFormat("  File \"%U\", line %d, in %U: ?\n",
+                                        filename, lineno, name);
+        }
+        else
+        {
+            line = PyUnicode_FromFormat("  File \"%U\", line %d, in %U: %S\n",
+                                        filename, lineno, name, formatted);
+            Py_DECREF(formatted);
+        }
+    }
     if (line == NULL)
         return -1;
     err = PyFile_WriteObject(line, f, Py_PRINT_RAW);
@@ -376,10 +399,7 @@ tb_printinternal(PyTracebackObject *tb, 
     }
     while (tb != NULL && err == 0) {
         if (depth <= limit) {
-            err = tb_displayline(f,
-                                 tb->tb_frame->f_code->co_filename,
-                                 tb->tb_lineno,
-                                 tb->tb_frame->f_code->co_name);
+            err = tb_displayline(f, tb);
         }
         depth--;
         tb = tb->tb_next;