JavaScript vs Python

gistfile1.js

//JavaScript
function _A(num){
  var o = {};
  
  o.a = num;
  o.square = function(){
    return o.a * o.a;
  };
  
  return o;
}

a = new _A(10);
console.log(a.a); // 10

a.__proto__.b = 20;
console.log(a.b); // 20

a.b = 30
console.log(a.b); // 30

delete a.b;
console.log(a.b); // 20

function _B(){}

b = new _B()
console.log(b.a); // undefined

b.__proto__ = a;
console.log(b.square()); // 100

gistfile2.py

# Python
class A(object):
    def __init__(self, a):
        self.a = a
    
    def square(self):
        return self.a * self.a


a = A(10)
print(a.a) # 10

A.b = 20
print(a.b) # 20 - 'delegates' to A

a.b = 30
print(a.b) # 30

del a.b
print(a.b) # 20

class B(object):
    pass


b = B()
 
b.__class__ = A
print(b.square()) # 100 - 'delegates' to A