I am building a dashboard with Panel Holoviz using a Parameterized Class .
In this Class I would like a button that, when pushed starts training a model, and when the model is finished training, it needs to show a graph based on that model.
How do I build such dependencies in Panel using a Class?
The example below shows how when the button is pushed, it triggers 'button', which triggers method train_model(), which when finished, triggers method update_graph().
The key lies in the lambda x: x.param.trigger('button') and @param.depends('button', watch=True):
import numpy as np
import pandas as pd
import holoviews as hv
import param
import panel as pn
hv.extension('bokeh')
class ActionExample(param.Parameterized):
# create a button that when pushed triggers 'button'
button = param.Action(lambda x: x.param.trigger('button'), label='Start training model!')
model_trained = None
# method keeps on watching whether button is triggered
@param.depends('button', watch=True)
def train_model(self):
self.model_df = pd.DataFrame(np.random.normal(size=[50, 2]), columns=['col1', 'col2'])
self.model_trained = True
# method is watching whether model_trained is updated
@param.depends('model_trained', watch=True)
def update_graph(self):
if self.model_trained:
return hv.Points(self.model_df)
else:
return "Model not trained yet"
action_example = ActionExample()
pn.Row(action_example.param, action_example.update_graph)
Helpful documentation on the Action button:
https://panel.pyviz.org/gallery/param/action_button.html#gallery-action-button
Other helpful example of Action param:
https://github.com/pyviz/panel/issues/239
BEFORE pushing button: