Exception confusion

[Martin Sjögren]

On Wed, Aug 08, 2001 at 01:41:10PM +0200, Martin von Loewis wrote:
> Martin Sjögren <martin at strakt.com> writes:

[snip]

> III. Raising an exception in the form klass,value is the same
>      as raising it as klass(value)

On the contrary, it isn't!

You're saying that 'raise Exception, var' is the same as 'Exception(var)',
but what about these two examples:

  raise Exception, 'foo'

This is most certainly equivalent to "Exception('foo')" in that this
holds:
  Exception('foo').args == ('foo',)

No worries there!

  raise Exception, ('foo', 'bar')

What happens now?  This is NOT equivalent to "Exception(('foo', 'bar'))"
since:
  Exception(('foo', 'bar')) == (('foo', 'bar'),)
whereas "raise Exception, ('foo', 'bar') yields the tuple ('foo', 'bar')
as exc.arg!

[snip more]

All I'm asking is WHY tuples are handled differently?  In my case I have
an exception that may be raised either with a tuple or a string. Right now
I have to do this:

except MyException, exc:
    if len(exc.args) == 0:
        arg = None
    elif len(exc.args) == 1:
        arg = exc.args[0]
    else:
        arg = exc.args

Why-oh-why do exceptions work like this? :(

Martin

-- 
Martin Sjögren
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