On Fri, Feb 14, 2014 at 7:04 PM, Chris Withers <ch...@simplistix.co.uk> wrote:
>
> To implement __lt__ in Python 2, I could do:
>
> def __lt__(self, other):
> if not isinstance(other, Range):
> return True
> return ((self._lower, self._upper, self._bounds) <
> (other._lower, other._upper, other._bounds))
>
> Because None < 1 raises a TypeError, in Python 3 I have to do:
>
> def __lt__(self, other):
> if not isinstance(other, Range):
> return NotImplemented
> for attr in '_lower', '_upper', '_bounds':
> self_value = getattr(self, attr)
> other_value = getattr(other, attr)
> if self_value == other_value:
> pass
> elif self_value is None:
> return True
> elif other_value is None:
> return False
> else:
> return self_value < other_value
> return False
>
> Am I missing something? How can I get this method down to a sane size?
Can you be certain that all your values are either None or positive
integers? If so, try this:
def __lt__(self, other):
if not isinstance(other, Range):
return True # or NotImplemented, not sure why this change
return ((self._lower or 0, self._upper or 0, self._bounds or 0) <
(other._lower or 0, other._upper or 0, other._bounds or 0))
That'll treat all Nones as 0, and compare them accordingly. If you
can't depend on them being positive (eg if you need None to be less
than 0 rather than equal - even more so if you need it to be less than
negative numbers), you'll need to more explicitly check. But this is
nice and tidy, if it works.
ChrisA
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