Python logging using a decorator

This is the first example we meet when we face with decorators. But I'm not able to realize what exactly I would like.

A simple decorator named LOG. It should work like this:

@LOG
def f(a, b=2, *c, **d):
    pass

And the result should be something like:

f(1, pippo=4, paperino='luca')
===== Enter f =====
a = 1
b = 2
pippo = 4
paperino = luca
===== Exit f =====

Where every argument passed as a parameter to the function is showed with its value.

I discovered that the problem is harder than I thought, mainly because of the many different ways you can pass arguments to a function (think about tuples with *c or dictionaries with **d).

I tried a solution but I'm not sure it's correct. It' somethink like this:

def LOG(fn):
    import inspect
    varList, _, _, default = inspect.getargspec(fn)
    d = {}
    if default is not None:
        d = dict((varList[-len(default):][i], v) for i, v in enumerate(default))
    def f(*argt, **argd):
        print ('Enter %s' % fn).center(100, '=')
        d.update(dict((varList[i], v) for i, v in enumerate(argt)))
        d.update(argd)
        for c in d.iteritems():
            print '%s = %s' % c
        ret = fn(*argt, **argd)
        print 'return: %s' % ret
        print ('Exit %s' % fn).center(100, '=')
        return ret
    return f

I think it's not so easy as I expected, but it's strange I didn't found what I wanted on Google.

Can you tell me if my solution is ok? Or can you suggest a better solution to the problem I proposed?

Thank you to everybody.