Using __Add__ Operator with Multiple Arguments in Python
I Am Trying to Add a Class Object with a Number, but I'm Confused on How to Go About Adding a Class Object with Two Numbers. for Example, This Is My...
I am trying to add a class object with a number, but I'm confused on how to go about adding a class object with two numbers. For example, this is my hypothetical add class method:
class A:
def __add__(self, b):
return something
I know how to add this so far:
a = A()
print(a + 1)
But, what if I want to add it like this?
a = A()
print(a + 1 + 2)
Should I use *args for the add class method?
4 Answers
No, you can't use multiple arguments. Python executes each + operator separately, the two + operators are distinct expressions.
For your example, object + 1 + 2 really is (object + 1) + 2. If (object + 1) produces an object that has an __add__ method, then Python will call that method for the second operator.
You could, for example, return another instance of A here:
>>> class A:
... def __init__(self, val):
... self.val = val
... def __repr__(self):
... return f'<A({self.val})>'
... def __add__(self, other):
... print(f'Summing {self} + {other}')
... return A(self.val + other)
...
>>> A(42) + 10
Summing A(42) + 10
<A(52)>
>>> A(42) + 10 + 100
Summing A(42) + 10
Summing A(52) + 100
<A(152)>
You would want your return value to be an object itself, that also supports the add operation, e.g.:
class A:
def __init__(self, value=0):
self.value = value
def __add__(self, b):
return A(self.value + b)
def __str__(self):
return str(self.value)
a = A()
print(a + 1 + 2)
Output:
3
It perfectly works even with multiple values since each add only adds two values (see the multiple + signs when you ad multiple values):
class A:
def __init__(self, value):
self.a = value
def __add__(self, another_value):
return self.a + another_value
a = A(1)
print(a+1+1)
you could always just do this:
>>> class A:
... def __init__(self, val):
... self.val = val
... def __repr__(self):
... return f'<A({self.val})>'
... def __add__(self, other):
... print(f'Summing {self} + {other}')
... return A(self.val + other)
...
>>> A(42) + 10
Summing A(42) + 10
<A(52)>
>>> A(42) + 10 + 100
Summing A(42) + 10
Summing A(52) + 100
<A(152)>>>> class A:
... def __init__(self, val):
... self.val = val
... def __repr__(self):
... return f'<A({self.val})>'
... def __add__(self, other):
... print(f'Summing {self} + {other}')
... return A(self.val + other)
...
>>> A(42) + 10
Summing A(42) + 10
<A(52)>
>>> A(42) + 10 + 100
Summing A(42) + 10
Summing A(52) + 100
<A(152)>
David Miller brings 15 years of experience in global economics, personal finance strategy, and market dynamics. He specializes in turning complex economic trends into actionable insights for everyday readers.
