Hi!

I have unsucessfully tried to define a default value by referencing other attributes. I'm sure the code below doesnt' work for some obvious or fundamental reason, but I would be grateful for comments on how to do something like it:

import attr
from attr.validators import instance_of
import datetime

@attr.s
class Something:
    some_date = attr.ib(validator=instance_of(datetime.date))
    some_number = attr.ib(convert=float)
    name = attr.ib(validator=instance_of(str),
                   default="Generic Name {0} - {1}%".format(
                       some_date.strftime("%d-%b-%Y"),
                       some_number * 100)
                   )

s = Something(some_date=datetime.date.today(), some_number=0.375)

I included the .strftime() conversion to highlight that name doesn't see a float and a date, but a _CountingAttr object, hence I get an AttributeError (and a TypeError for some_number * 100). Since I can't reference self either, what would be the correct way to do this?