On 2014-02-14 08:04, Chris Withers wrote:
Hi All,
Sending this to python-dev as I'm wondering if this was considered when
the choice to have objects of different types raise a TypeError when
ordered...
So, the concrete I case I have is implementing stable ordering for the
python Range objects that psycopg2 uses. These have 3 attributes that
can either be None or, for sake of argument, a numeric value.
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?
How about this:
def make_key(item):
return [(x is not None, x or 0) for i in [item._lower,
item._upper, item._bounds]]
def __lt__(self, other):
if not isinstance(other, Range):
return NotImplemented
return make_key(self) < make_key(other)
It'll make None less than any number.
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
