Initialization changes constant attribute.

[LinuxIsCool]

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ALL software version info

panel==1.4.0
param==2.1.0
Python 3.10.12

Description of expected behavior and the observed behavior

Expecting normal initialization. Unfortunately, constant is being set to False on my parameter.

I would expect invariant_coef to remain constant.

Complete, minimal, self-contained example code that reproduces the issue

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

class BondingCurve(pm.Parameterized):
    supply = pm.Number(80)
    reserve = pm.Number(40)
    kappa = pm.Number(2)
    invariant_coef = pm.Number(constant=True)
    price = pm.Number(constant=True)
    
    # def __init__(self, **params):
    #     super().__init__(**params)
    #     self.set_invariant_coef()
    
    @pm.depends(on_init=True, watch=True)
    def set_invariant_coef(self):
        with pm.edit_constant(self):
            self.invariant_coef = self.supply ** self.kappa / self.reserve

bc = BondingCurve()

pn.panel(bc)

bc.param['invariant_coef'].constant

False

[hoxbro]

This context manager seems to work not sure about what 'existing' does

import param as pm
import panel as pn
from contextlib import contextmanager


@contextmanager
def edit_constant(parameterized):
    """
    Temporarily set parameters on Parameterized object to constant=False
    to allow editing them.
    """
    params = parameterized.param.objects().values()  # changed from: 
    # params = parameterized.param.objects('existing').values()
    constants = [p.constant for p in params]
    for p in params:
        p.constant = False
    try:
        yield
    finally:
        for p, const in zip(params, constants):
            p.constant = const


class BondingCurve(pm.Parameterized):
    price = pm.Number(constant=True)

    @pm.depends(on_init=True, watch=True)
    def set_ex(self):
        with edit_constant(self):
            self.price = 1


bc = BondingCurve()

bc.param.price.constant, bc.price

[LinuxIsCool]

Hi is this a bug in the library?

Again, I'm trying to use constants and edit_constant but am having this bug with the library.

[philippjfr]

That does look like a bug, yes.