add more than two objects with add function

Question

I have a class it can successfully add two variables of object of class a

class a():
    def __add__(self, other):
        return self.val+other.val
    def __init__(self,a):
        self.val=a
aa=a(22)
bb=a(11)
aa+bb
33

But when I try to give it third object to add, it through error

cc=a(11)
aa+bb+cc
Traceback (most recent call last):
  File "<pyshell#43>", line 1, in <module>
    aa+bb+cc
TypeError: unsupported operand type(s) for +: 'int' and 'a'

It is because first two aa+bb return int and its add function is design to add object addition
Any one can suggest how I can add three objects

I find this link Using __add__ operator with multiple arguments in Python but it is working on one object and 2 integers. But I want to add three objects. and all these three combine and return integer

Asked By: Artier

||

Source

Answer 1

__add__ must return an instance of a class, not int

class a():
    def __add__(self, other):
        return a(self.val + other.val)
    def __init__(self, a):
        self.val = a

Answered By: todel23

Answer 2

Here’s an example of how __add__ and __radd__ should be implemented.

We have a class A that has an attribute n which is an integer. We want to be able to add classes of the same type and we also want to be able to add integer values. Therefore:

class A:
    def __init__(self, n):
        self._n = n
    @property
    def n(self):
        return self._n
    def __add__ (self, other):
        if isinstance(other, int):
            return A(self.n + other)
        assert isinstance(other, type(self))
        return A(self.n + other.n)
    def __radd__(self, other):
        assert isinstance(other, int)
        return A(self.n + other)
    def __str__(self):
        return f'{self.n}'
    def __repr__(self):
        return f'{self.n=}'

a = A(1)
b = A(2)
c = A(3)

print(10+a+10+b+10+c+10)

c += 5
print(c)
print(c.n)

Output:

46
8
8

Answered By: Stuart

Answer 3

This is what I looking for

class a():
    def __add__(self, other):
        return a(self.val+other.val)
    def __init__(self,a):
        self.val=a
aa=a(22)
bb=a(11)
cc=a(11)
d=aa+bb+cc
print(d.val)

Out put

44

Answered By: Artier

add more than two objects with add function

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add more than two objects with __add__ function

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add more than two objects with add function