Overriding Built-in Methods

Last but not least, let's take a look at some of the built-in methods we can override in Python. While there isn't a default behavior for the arithmetic operators like we just saw, there is a default behavior for printing a class instance:

class Point:
    def __init__(self, x: int, y: int) -> None:
        self.x = x
        self.y = y


p1 = Point(4, 5)
print(p1)
# <Point object at 0xa0acf8>

That's not super useful! We probably want to see the fields!

Let's teach our Point class to print itself. The __str__ method (short for "string") lets us do just that. It takes no inputs but returns a string that will be printed to the console when someone passes an instance of the class to Python's print() function.

class Point:
    def __init__(self, x: int, y: int) -> None:
        self.x = x
        self.y = y

    def __str__(self) -> str:
        return f"({self.x},{self.y})"


p1 = Point(4, 5)
print(p1)
# prints "(4,5)"