Simple example for Param Panel class interactions

example.py

## Run it on jupyter notebook for interactive panel
import param as pm
import panel as pn
pn.extension()

class A(pm.Parameterized):
    a = pm.Number(2, step=1)
    
    def get_a_squared(self):
        return self.a * self.a

class B(pm.Parameterized):
    def __init__(self, a:A, **params):
        super().__init__(**params)
        self.a = a
        
    b = pm.Number(2, step=1)
    
    @pm.depends('a.a', 'b') # a.param also works
    def sum(self):
        return self.a.a + self.b     
    
    @pm.depends('a.get_a_squared', 'b') # a.param also works
    def sum_of_squares(self):
        return self.a.get_a_squared() + (self.b*self.b)

    
a = A()
b = B(a)

pn.Row(
    pn.Column(a, b),
    pn.Column('Sum: ', b.sum, 'Sum of Squares:', b.sum_of_squares)
)
## Result
## changing parameter a and b should reflect change in sum and its squares

Good base case to remember. Thanks @bhargavkakadiya