Access instance variable from one instance to another

Question

I am learning python. Suppose I have my Class named Dog, and two instances named Fido and Molly. I want to change an attribute of second instance by overloading + operator with __add__ so when I type Fido+Molly the Molly.touched attribute will be set. How is accessing from one instance to another instance's attributes deployed in python?

pylang · Accepted Answer · 2016-11-19 13:32:02Z

3

I think you are interested in how the __add__ special method works. In essence it works as x.__add__(y) where x and y can be instance objects. See an example of it's implementation here.

You would need to overload __add__() in Dog to return something that updates the y.touched attribute. Example:

class Dog(object):

    def __init__(self, touched):
        self.touched = touched

    def __add__(self, other):
        other.touched = other.touched + self.touched 
        #return None                                    # optional, explicit

fido = Dog(1)
molly = Dog(2)

fido + molly
molly.touched
# 3

edited Nov 19, 2016 at 13:32

answered Nov 19, 2016 at 12:33

pylang

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2 Comments

TigerhawkT3 Over a year ago

return None is redundant, by the way.

pylang Over a year ago

Yes, but it is explicit for someone unfamiliar with Python. I will make a comment

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