>> >>> x = (1, 2, 3) >> >>> x += (4, 5, 6) Gustavo> Hey, shouldn't this raise an exception? Perhaps it should, but it doesn't: If x is a tuple, x += y is equivalent to x = x + y which creates a brand-new object and (re)binds x to it. -- Andrew Koenig, ark at research.att.com, http://www.research.att.com/info/ark