On 7 November 2012 13:39, Joshua Landau <joshua.landau...@gmail.com> wrote: > > On 7 November 2012 11:11, Oscar Benjamin <oscar.j.benja...@gmail.com> wrote: >> >> A more modest addition for the limited case described in this thread could >> be to use exponentiation: >> >> >>> [0] ** (2, 3) >> [[0, 0, 0], [0, 0, 0]] > > Hold on: why not just use multiplication? > >>>> [0] * (2, 3) > > is an error now, and it makes total sense. Additionally, it's not breaking > the "no copy -- _ever_" rule because none of the lists existed before. The > values inside the list would be by reference, as before, so lst * (x,) would > be the same as lst * x if x is an integer.
The problem is that this operation is asymmetric. Currently int/list multiplication is commutative so that: ['a', 'b'] * 2 == 2 * ['a', 'b'] If you use this kind of multiplication what happens to the other cases? e.g. what do you give for: >>> [0] * [2, 3] >>> [2, 3] * [0] >>> (2, 3) * [0] >>> (2, 3) * (4, 5) and so on. Although Python does not guarantee commutativity of multiplication in general I think that since for lists it has always been commutative it would be bad to change that. Exponentiation is expected to be asymmetric and is currently unused so there is no ambiguity. The problem is if someone has already subclassed list and added an exponentiation method. Oscar -- http://mail.python.org/mailman/listinfo/python-list
