__future__ and __rdiv__

Massimo Di Pierro massimo.dipierro at gmail.com
Mon Jan 23 01:17:54 EST 2012

Thank you. I tried __rtruediv__ and it works.

On Jan 23, 2012, at 12:14 AM, Ian Kelly wrote:

> On Sun, Jan 22, 2012 at 10:22 PM, Massimo Di Pierro <massimo.dipierro at gmail.com> wrote:
> Hello everybody,
> I hope somebody could help me with this problem. If this is not the right place to ask, please direct me to the right place and apologies.
> I am using Python 2.7 and I am writing some code I want to work on 3.x as well. The problem can be reproduced with this code:
> # from __future__ import division
> class Number(object):
>    def __init__(self,number):
>        self.number=number
>    def __rdiv__(self,other):
>        return other/self.number
> print 10/Number(5)
> It prints 2 as I expect. But if I uncomment the first line, I get:
> Traceback (most recent call last):
>  File "test.py", line 8, in <module>
>    print 10/Number(5)
> TypeError: unsupported operand type(s) for /: 'int' and 'Number'
> Is this a bug or the __future__ division in 3.x changed the way operators are overloaded? Where can I read more?
> In Python 3, the / operator uses __truediv__ and the // operator uses __floordiv__.
> In Python 2, the / operator uses __div__, unless the future import is in effect, and then it uses __truediv__ like Python 3.
> http://docs.python.org/reference/datamodel.html#emulating-numeric-types
> Cheers,
> Ian

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