How to watch all of the parameters of list items?

Panel
1

In the following code, I would like b.view to update when any of the a values are updated.

import param as pm
import panel as pn
pn.extension()
class A(pm.Parameterized):
    a = pm.Integer(0)
        
class B(pm.Parameterized):
    a_list = pm.List(class_=A)

    def sum_a_list(self):
        return sum([a.a for a in self.a_list])
    
    @pm.depends('a_list')
    def view(self):
        return pn.Row(self, self.sum_a_list)

a1 = A(a=1)
a2 = A(a=2)
b = B(a_list=[a1,a2])
pn.Column(a1, a2, b.view)

Does anyone know how this can be achieved?

Thanks!

2

With a little help from chatgpt I was able to achieve this functionality:

import param as pm
import panel as pn
pn.extension()

class A(pm.Parameterized):
    a = pm.Integer(0)

class B(pm.Parameterized):
    a_list = pm.List(class_=A)
        
    @pm.depends('a_list', watch=True, on_init=True)
    def _update_watchers(self):
        for a in self.a_list:
            # Watch the 'a' parameter of each instance in a_list
            a.param.watch(self._on_a_change, 'a')

    def _on_a_change(self, event):
        # Trigger an update when 'a' changes
        self.param.trigger('a_list')

    def sum_a_list(self):
        return sum([a.a for a in self.a_list])

    @pm.depends('a_list')
    def view(self, *args):  # Modified to accept *args
        return pn.Column(*self.a_list, self, self.sum_a_list())

a1 = A(a=1)
a2 = A(a=2)
b = B(a_list=[a1, a2])

pn.Column(b.view)

Is there a more straightforward way of doing it?

3

I’m having performance issues with the above.