ERROR: 'Document' object has no attribute '_callbacks'

[MarcSkovMadsen]

I've just installed Panel from scratch according to the developer guide https://panel.holoviz.org/developer_guide/index.html.

When I panel serve 'script.py' --autoreload --show I get

ERROR: 'Document' object has no attribute '_callbacks'

(I installed this from scratch as I got the same error in my existing installation).

script.py

import panel as pn
import pandas as pd
import param

pn.extension()

data = pd.DataFrame()

class MyDataClass(param.Parameterized):
    data = param.DataFrame()

my_data = MyDataClass()

button = pn.widgets.Button(name="UPDATE")

@param.depends(button.param.value)
def update(value):
    my_data.data = pd.DataFrame({"x": [1]*10})

pn.Column("# Test", pn.Param(my_data), button).servable()

[maximlt]

What version of bokeh do you have?

[maximlt]

Without #2741 being merged it's likely that you end up with a 2.3 version instead of the actually required 2.4 one.

[hoxbro]

I'm having the same problem and I'm running on master branch of panel and bokeh version 2.4.0. The problem only happens when running panel serve with --autoreload. The error is coming from:

panel/panel/command/serve.py

Line 39 in 80a66c3

doc._callbacks[None] = {}

[philippjfr]

Damn, looks like we indeed missed a compatibility change with Bokeh 2.4 and will likely have to release another patch release (i.e. 0.12.4).