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Fri Feb 14 09:04:29 CET 2014 · https://mail.python.org/pipermail/python-dev/2014-February/132332.html

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?

cheers,

Chris

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[Python-Dev] python 3 niggle: None < 1 raises TypeError