How to return a default attribute for a class' instance?

Question

I have a class with the following structure:

class Example:
    def __init__(self, value, foo):
        self.value = value
        self.foo = foo
        self.bar = self.modify_stuff(value, foo)

    def modify_stuff(self, value, foo):
        """ some code """
        pass

I want to create an instance of the class, and then be able to refer to value directly, like this:

ex = Example(3, 'foo')
ans = 5 + ex

Instead of:

ans = 5 + ex.value

How can I do this?

Python doesn't do implicit conversions, period. It's literally in the zen. The best you can do is manually implement __add__/__radd__/etc to have the appropriate behavior — Brian61354270
– Brian61354270, Commented Jul 1, 2022 at 2:51
@Brian, but what about pandas.DataFrame? if I create something like df = pd.DataFrame([1, 2, 3, 4]) I can access the data directly from df (like df + 5), I don't need to do something like df.data + 5 — fjsh
– fjsh, Commented Jul 1, 2022 at 2:56
Yes, because pandas manually implemented __add__/__radd__/etc to have the appropriate behavior. — Brian61354270
– Brian61354270, Commented Jul 1, 2022 at 2:58

maya · Accepted Answer · 2022-07-01 02:56:32Z

1

Rewrite the add and radd:

class Example:
    def __init__(self, value):
        self.value = value

    def __add__(self, other):
        if isinstance(other, Example):
            return self.value + other.value

        return self.value + other

    def __radd__(self, other):
        if isinstance(other, Example):
            return self.value + other.value

        return self.value + other


print(Example(3) + 5)
print(Example(4) + Example(2))

# 8
# 6

answered Jul 1, 2022 at 2:56

maya

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2 Comments

Farshid Over a year ago

Cool things you learn everyday!

maya Over a year ago

Learning from each other ^u^

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