On Mon, Nov 19, 2012 at 4:16 AM, D'Arcy J.M. Cain <da...@druid.net> wrote: > On 18 Nov 2012 16:50:52 GMT > Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: >> On Sun, 18 Nov 2012 08:53:25 -0500, Roy Smith wrote: >>> > Use a list when you need an ordered collection which is mutable >> > (i.e. can be altered after being created). Use a tuple when you >> > need an immutable list (such as for a dictionary key). >> >> I keep hearing about this last one, but I wonder... who *actually* >> does this? I've created many, many lists over the years -- lists of >> names, lists of phone numbers, lists of directory search paths, all >> sorts of things. I've never needed to use one as a dictionary key. > > Well, as long as *you* never needed it then... > > CellBlock = 9 # There's a riot going on... > Cell = 17 > Bunk = "top" > > Prisoner = {(CellBlock, Cell, Bunk): "Bernie Madoff"}
That's a structure, not a list. Every key will consist of precisely three values: two integers and one keyword string. Already covered by a previous example. ChrisA -- http://mail.python.org/mailman/listinfo/python-list