__div__ not recognized automatically

[Anton81]

Hello!

I wrote a class

class NumX:
...
def __add__(self,ot her):
...
def __div__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
...

Somewhere else I use

a=(b+c)/2

where all variables are of NumX Type. When I execute the program it
complains that it can't find an operator "/" for "instance" and "integer".
However if I use pdb the same command works when started on the prompt. Also
the manual execution

a=(b+c).__div__ (2)

works. Any suggestions what goes wrong?

Anton

[Steven D'Aprano]

Re: __div__ not recognized automatically

On Thu, 02 Nov 2006 12:59:32 +0100, Anton81 wrote:

When I execute the program it
complains that it can't find an operator "/" for "instance" and "integer".

How about if you post the actual traceback you get, rather than
paraphrasing? That way, we don't have to guess.


--
Steven.

[Nick Craig-Wood]

Re: __div__ not recognized automatically

Anton81 <usenet1@anton. e4ward.comwrote :

class NumX:
...
def __add__(self,ot her):
...
def __div__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
...
>
Somewhere else I use
>
a=(b+c)/2
>
where all variables are of NumX Type. When I execute the program it
complains that it can't find an operator "/" for "instance" and "integer".
However if I use pdb the same command works when started on the prompt. Also
the manual execution
>
a=(b+c).__div__ (2)
>
works. Any suggestions what goes wrong?

Post some code which actually demonstrates the problem.

Eg, change this code until it does demonstrate the problem

------------------------------------------------------------
class NumX(object):
def __init__(self, value):
self.value = long(value)

def __add__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
return NumX(self.value + other.value)

def __div__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
return NumX(self.value / other.value)

def __str__(self):
return "%s(%s)" % (self.__class__ .__name__, self.value)

a = NumX(4)
b = NumX(2)

print a,b
print a+b
print (a+b)/2
------------------------------------------------------------

This prints

------------------------------------------------------------
NumX(4) NumX(2)
NumX(6)
NumX(3)
------------------------------------------------------------

--
Nick Craig-Wood <nick@craig-wood.com-- http://www.craig-wood.com/nick

[Peter Otten]

Re: __div__ not recognized automatically

Anton81 wrote:

Hello!
>
I wrote a class
>
class NumX:
...
def __add__(self,ot her):
...
def __div__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
...
>
Somewhere else I use
>
a=(b+c)/2
>
where all variables are of NumX Type. When I execute the program it
complains that it can't find an operator "/" for "instance" and "integer".
However if I use pdb the same command works when started on the prompt.
Also the manual execution
>
a=(b+c).__div__ (2)
>
works. Any suggestions what goes wrong?

If you have the

from __future__ import division

statement, you need to override __truediv__(), not __div__()

Peter

[Tuomas]

Re: __div__ not recognized automatically


Try
a=(b+c)/NumX(2)

TV

Anton81 wrote:

Hello!
>
I wrote a class
>
class NumX:
...
def __add__(self,ot her):
...
def __div__(self,ot her):
if not isinstance(othe r,NumX): other=NumX(othe r)
...
>
Somewhere else I use
>
a=(b+c)/2
>
where all variables are of NumX Type. When I execute the program it
complains that it can't find an operator "/" for "instance" and "integer".
However if I use pdb the same command works when started on the prompt. Also
the manual execution
>
a=(b+c).__div__ (2)
>
works. Any suggestions what goes wrong?
>
Anton

[Anton81]

Re: __div__ not recognized automatically

If you have the

>
from __future__ import division
>
statement, you need to override __truediv__(), not __div__()

That worked after I also added
from __future__ import division
to all other modules I created.

Is it possible that there appears an inconsistency if the division is
imported in only some of the modules?

Anton

[Peter Otten]

Re: __div__ not recognized automatically

Anton81 wrote:

>If you have the
>>
>from __future__ import division
>>
>statement, you need to override __truediv__(), not __div__()

>
That worked after I also added
from __future__ import division
to all other modules I created.
>
Is it possible that there appears an inconsistency if the division is
imported in only some of the modules?

Yes. If you use your class with and without the __future__ option you have
to implement both __div__ and __truediv__, I suppose.

Peter