Kay Schluehr wrote: > I want to manipulate a deeply nested list in a generic way at a > determined place. Given a sequence of constant objects a1, a2, ..., aN > and a variable x. Now construct a list from them recursively: > > L = [a1, [a2, [....[aN, [x]]...]] > > The value of x is the only one to be changed. With each value of x a > new instance of L is needed so that we actually have a function: > > L = lambda x: [a1, [a2, [....[aN, [x]]...]] > > I'm seeking for an efficient implementation that does not recompute the > whole list each time. Any ideas?
I'd say you are nesting the wrong way. >>> items = make_list(range(10)) >>> def make_list(items): ... return reduce(lambda *args: args, items) ... >>> def update_value(items, value): ... return items[0], value ... >>> items = make_list(range(10)) >>> items (((((((((0, 1), 2), 3), 4), 5), 6), 7), 8), 9) >>> update_value(items, 42) (((((((((0, 1), 2), 3), 4), 5), 6), 7), 8), 42) Obviously I must be missing something. What? Peter -- http://mail.python.org/mailman/listinfo/python-list
