Subclass

2 snippets across 2 stacks — JavaScript, Python

JSJavaScript

Inheritance (extends)

syntax

class Child extends Parent {
  constructor(params) {
    super(parentParams);
  }
}

example

class Shape {
  constructor(color) {
    this.color = color;
  }
  describe() {
    return `A ${this.color} shape`;
  }
}

class Circle extends Shape {
  constructor(color, radius) {
    super(color);
    this.radius = radius;
  }
  get area() {
    return Math.PI * this.radius ** 2;
  }
  describe() {
    return `A ${this.color} circle (r=${this.radius})`;
  }
}

const c = new Circle("blue", 5);
console.log(c.describe());
console.log(c.area.toFixed(2));

output

"A blue circle (r=5)"
"78.54"

Note super() must be called in the child constructor before accessing this. Methods can be overridden. Use super.method() to call the parent version.

PYPython

Inheritance & super()

PY · Classes & OOP

syntax

class Child(Parent):
    def __init__(self):
        super().__init__()

example

class Vehicle:
    def __init__(self, make: str, year: int):
        self.make = make
        self.year = year

class ElectricCar(Vehicle):
    def __init__(self, make: str, year: int, range_km: int):
        super().__init__(make, year)
        self.range_km = range_km

    def __repr__(self) -> str:
        return f"{self.year} {self.make} ({self.range_km}km range)"

car = ElectricCar("Tesla", 2026, 600)
print(car)

output

2026 Tesla (600km range)

Note Always call super().__init__() in the child to ensure the parent is properly initialized. Python supports multiple inheritance via MRO (Method Resolution Order).