diff -r e539761d45e3 -r a1bb43bbf797 Include/frameobject.h
--- a/Include/frameobject.h	Thu Nov 14 15:35:47 2013 +0100
+++ b/Include/frameobject.h	Thu Nov 14 18:02:26 2013 +0100
@@ -41,6 +41,7 @@ typedef struct _frame {
 
     PyThreadState *f_tstate;
     int f_lasti;                /* Last instruction if called */
+    PyObject *f_annotation;     /* shown in traceback */
     /* Call PyFrame_GetLineNumber() instead of reading this field
        directly.  As of 2.3 f_lineno is only valid when tracing is
        active (i.e. when f_trace is set).  At other times we use
diff -r e539761d45e3 -r a1bb43bbf797 Lib/traceback.py
--- a/Lib/traceback.py	Thu Nov 14 15:35:47 2013 +0100
+++ b/Lib/traceback.py	Thu Nov 14 18:02:26 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 in extracted_list:
+        item = '  File "{}", line {}, in {}'.format(filename, lineno, name)
+        if annotation is not None:
+            item += ': {}'.format(annotation)
+        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 = f.f_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)
         curr = next_item
         n += 1
 
@@ -310,3 +314,16 @@ 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 wrapped(*args, **kwargs):
+            try:
+                f(*args, **kwargs)
+            except Exception as exc:
+                frame = exc.__traceback__.tb_next.tb_frame
+                annotation = format.format(**frame.f_locals)
+                frame.f_annotation = annotation
+                raise
+        return wrapped
+    return wrapper
diff -r e539761d45e3 -r a1bb43bbf797 Objects/frameobject.c
--- a/Objects/frameobject.c	Thu Nov 14 15:35:47 2013 +0100
+++ b/Objects/frameobject.c	Thu Nov 14 18:02:26 2013 +0100
@@ -15,6 +15,7 @@ static PyMemberDef frame_memberlist[] = 
     {"f_builtins",      T_OBJECT,       OFF(f_builtins),  READONLY},
     {"f_globals",       T_OBJECT,       OFF(f_globals),   READONLY},
     {"f_lasti",         T_INT,          OFF(f_lasti),     READONLY},
+    {"f_annotation",    T_OBJECT,       OFF(f_annotation), 0},
     {NULL}      /* Sentinel */
 };
 
@@ -442,6 +443,7 @@ frame_dealloc(PyFrameObject *f)
     Py_CLEAR(f->f_exc_type);
     Py_CLEAR(f->f_exc_value);
     Py_CLEAR(f->f_exc_traceback);
+    Py_CLEAR(f->f_annotation);
 
     co = f->f_code;
     if (co->co_zombieframe == NULL)
@@ -473,6 +475,7 @@ frame_traverse(PyFrameObject *f, visitpr
     Py_VISIT(f->f_exc_type);
     Py_VISIT(f->f_exc_value);
     Py_VISIT(f->f_exc_traceback);
+    Py_VISIT(f->f_annotation);
 
     /* locals */
     slots = f->f_code->co_nlocals + PyTuple_GET_SIZE(f->f_code->co_cellvars) + PyTuple_GET_SIZE(f->f_code->co_freevars);
@@ -506,6 +509,7 @@ frame_tp_clear(PyFrameObject *f)
     Py_CLEAR(f->f_exc_type);
     Py_CLEAR(f->f_exc_value);
     Py_CLEAR(f->f_exc_traceback);
+    Py_CLEAR(f->f_annotation);
     Py_CLEAR(f->f_trace);
 
     /* locals */
@@ -730,6 +734,7 @@ PyFrame_New(PyThreadState *tstate, PyCod
 
     f->f_lasti = -1;
     f->f_lineno = code->co_firstlineno;
+    f->f_annotation = NULL;
     f->f_iblock = 0;
     f->f_executing = 0;
     f->f_gen = NULL;
diff -r e539761d45e3 -r a1bb43bbf797 Python/traceback.c
--- a/Python/traceback.c	Thu Nov 14 15:35:47 2013 +0100
+++ b/Python/traceback.c	Thu Nov 14 18:02:26 2013 +0100
@@ -343,15 +343,20 @@ int
 }
 
 static int
-tb_displayline(PyObject *f, PyObject *filename, int lineno, PyObject *name)
+tb_displayline(PyObject *f, PyObject *filename, int lineno, PyObject *name,
+               PyObject *annotation)
 {
     int err;
     PyObject *line;
 
     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
+        line = PyUnicode_FromFormat("  File \"%U\", line %d, in %U: %U\n",
+                                    filename, lineno, name, annotation);
     if (line == NULL)
         return -1;
     err = PyFile_WriteObject(line, f, Py_PRINT_RAW);
@@ -379,7 +384,8 @@ tb_printinternal(PyTracebackObject *tb, 
             err = tb_displayline(f,
                                  tb->tb_frame->f_code->co_filename,
                                  tb->tb_lineno,
-                                 tb->tb_frame->f_code->co_name);
+                                 tb->tb_frame->f_code->co_name,
+                                 tb->tb_frame->f_annotation);
         }
         depth--;
         tb = tb->tb_next;