Operator overloading python

Question

> class divnum:
>     def __init__(self,num):
>         self.nums=num
>     def __div__(self,other):
>         return self.nums/other.nums 
> a=divnum(5)  
> b=divnum(1)
> answer= (a/b)

This error "builtins.TypeError: unsupported operand type(s) for /: 'divnum' and 'divnum'". what i wrong?

Probably python version 3.x Since it would do float division by default, which is implemented by __truediv__ — M4rtini
– M4rtini, Commented Feb 8, 2014 at 1:40
Why was this downvoted? It's a perfectly reasonable beginner question, and one on which it's easy to be misled by lots of examples on the web which are Py 2-centric. — DSM
– DSM, Commented Feb 8, 2014 at 2:22
@user3286067 if M4rtini answer helped you, please consider accepting it as the answer by clicking on the "v" at the left of it. This way, future readers will know it is the correct solution. — brandizzi
– brandizzi, Commented Feb 8, 2014 at 2:36

M4rtini · Accepted Answer · 2014-02-08 02:18:14Z

2

Assuming this is Python 3.x

To implement the division operator for a class, there are two methods: __floordiv__ and __truediv__. integer and float division respectively.

If you only implement one of them, you get the TypeError you experienced when trying to do the other.

In python 3.x the default is float division, unless you use //. So you should implement __truediv__ in your class unless you only want integer division to be possible.

I don't have python 3.x myself, so i can't test this. But i think this should be right.

class divnum:
    def __init__(self,num):
         self.nums=num
    def __truediv__(self,other):
         return self.nums/other.nums

    def __floordiv__(self, other):
        return self.nums//other.nums

edited Feb 8, 2014 at 2:18

answered Feb 8, 2014 at 1:47

M4rtini

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2 Comments

user2357112 Over a year ago

__truediv__ and __floordiv__, not __truediv__ and __div__.

user3286067 Over a year ago

Thank you for answer. I can run truediv. Thank you very much

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