Comparing equality of classes with a variable number of attributes

[edoardob90]

In the Intro Tutorial's notebook on Object-oriented, we explored Python's special methods, like __eq__ to define the behavior or the equality operator with custom classes. Example

class Rectangle:
    def __init__(self, width, height):
        self.width = width
        self.height = height
        
    def area(self):
        return self.width * self.height
    
    def perimeter(self):
        return 2 * (self.width + self.height)
    
    def __str__(self):
        return f'Rectangle (width={self.width}, height={self.height})'
    
    def __repr__(self):
        return self.__str__()
    
    def __eq__(self, other):
        if isinstance(other, Rectangle):
            return (self.width, self.height) == (other.width, other.height)
        else:
            return False

But what if I have a class with a variable number of attributes? How can I write a __eq__ method? The key is the vars() built-in function, which for an object tries to call the method __dict__. From the docs: "A dictionary or other mapping object used to store an object’s (writable) attributes." Based on that, here's an example class where we can use vars() and __dict__ to define __eq__ even if we don't know how many attributes we have:

class Point:
    
    def __init__(self, *_, **kwargs):
        for k, v, in kwargs.items():
            setattr(self, k, v)

    def __repr__(self):
        sattr = ", ".join(str(getattr(self, x)) for x in self.__dict__)
        return f"Point({sattr})"

    def __eq__(self, other):
        if not isinstance(other, type(self)):
            return NotImplemented
        
        return vars(self) == vars(other)