I think it would be useful to sometimes have local variable
values printed with tracebacks and stack frames.  The
attached patch is a first cut at that.  I don't know if
people would want that as the default, so I've defaulted
argument printing to disabled.  With arg printing enabled,
executing this script:

#!/usr/bin/env python

import sys
import traceback

def exch(ty, val, tb):
    traceback.print_exception(ty, val, tb, args=True)
sys.excepthook = exch

def f(n,d):
    return n/d

def g(a):
    return a/(a-1)

for i in range(5,-1,-1):
    print g(i)

displays this output:

1
1
1
2
Traceback (most recent call last):
  File "/Users/skip/tmp/tb.py", line 17, in ?
    print g(i)
       exch: <function exch at 0x4c46b0>
       f: <function f at 0x441330>
       g: <function g at 0x441370>
       i: 1
  File "/Users/skip/tmp/tb.py", line 14, in g
    return a/(a-1)
       a: 1
ZeroDivisionError: integer division or modulo by zero

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user_id=51702

I like this idea alot! I usually debug by inserting print
"somevar
=",somevar around where I think the problem code is and this
patch
basically does it automagically for me. I can definitely
image this
patch saving me many hours of debug time. But:

1. It outputs to much information. An unhandled exception
that bubbles
   up can be 3-4 stackframes long and seeing all the
variables in
   those frames is excessive.

2. I think it would be better if the enhanced traceback was
either
   default or activated with a commandline option to Python.

Item 1 maybe can be solved by only outputting those names
that are
contained in the lines in which the exception is raised? So
that the
output in your example becomes:

Traceback (most recent call last):
  File "exception.py", line 20, in ?
    print g(i)
       g: <function g at 0x402efed4>
       i: 1
  File "exception.py", line 14, in g
    return a/(a-1)
       a: 1
ZeroDivisionError: integer division or modulo by zero

It feels a little weird to have to hook sys.excepthook. I
think this
idea is to good to be "buried" like that. Hopefully, with some
polishing it can be activated with a commandline option or
become the
default bahaviour. 

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Philipp Eby commented that he would not like to see this as
a default, as the default already prints too much
information. He also (indirectly) suggested that he would
not like to see it as a command line option, but that he
would prefer to see a different command line option instead
which enters pdb on uncaught exceptions.

Maybe this could be enabled only on the interactive interpreter? 

Skip's patch includes tests and docs, needs updating.

It would certainly be horrible to enable this by default. Think about
intermediate functions having 10 local variables each, most of which are
totally irrelevant.

How about reformulating it as a function appropriate as sys.excepthook?

If it becomes a sys.excepthook, it doesn't need to be part of Python
anymore; any user could install it as a recipe if they desire.

Hence I'm rejecting the patch.

Martin> If it becomes a sys.excepthook, it doesn't need to be part of
    Martin> Python anymore; any user could install it as a recipe if they
    Martin> desire.

    Martin> Hence I'm rejecting the patch.

It could still be a nice addition to the traceback module:

    sys.excepthook = traceback.verbose_traceback

In fact, a minimalist traceback style, similar to the one asyncore, might
also be useful:

    sys.excepthook = traceback.minimal_traceback

Skip

> It could still be a nice addition to the traceback module:

If it doesn't have to be in the standard library, I'd rather see it
as a cookbook recipe, or PyPI package. I think the debate is still
open whether, as an addition to traceback module, it would be "nice".

PyPI: http://pypi.python.org/pypi/tb