Operator overloading in python with the object on the right hand side of the operator

operator-overloading, python

Solution

Yes. For example, there is `__radd__`. Also, there are none for `__le__()`, `__ge__()`, etc., but as Joel Cornett rightly observes, if you define only `__lt__`, `a > b` calls the `__lt__` function of `b`, which provides a workaround.

>>> class My_Num(object):
...     def __init__(self, val):
...         self.val = val
...     def __radd__(self, other_num):
...         if isinstance(other_num, My_Num):
...             return self.val + other_num.val
...         else:
...             return self.val + other_num
... 
>>> n1 = My_Num(1)
>>> n2 = 3
>>> 
>>> print n2 + n1
4
>>> print n1 + n2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'My_Num' and 'int'

Note that in at least some cases it's reasonable to do something like this:

>>> class My_Num(object):
...     def __init__(self, val):
...         self.val = val
...     def __add__(self, other_num):
...         if isinstance(other_num, My_Num):
...             return self.val + other_num.val
...         else:
...             return self.val + other_num
...     __radd__ = __add__

Problem

I recently learned about operator overloading in python and I would like to know if the following is possible. Consider the following hypothetical/contrived class. ``` class My_Num(object): def __init__(self, val): self.val = val def __add__(self, other_num): if isinstance(other_num, My_Num): return self.val + other_num.val else: return self.val + other_num ``` I know that the way that's written above, I can do things like this ``` n1 = My_Num(1) n2 = My_Num(2) n3 = 3 print n1 + n2 print n1 + n3 ``` and those will work as expected. I also know that the way it's currently written I can't do this ``` n1 = My_Num(1) n2 = 2 print n2 + n1 ``` Is there any way around this? I know this example is contrived but I have an application in which it would be very useful if when I did operator overloading, the class for which I define the operator can appear on the right hand side of operator. Is this possible in python?

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