import panel as pn
import param


class Dashboard(param.Parameterized):
    file_selector = param.FileSelector()
    progress = pn.widgets.Progress(active=False)

    @param.depends("file_selector", watch=True)
    def activate_upload_status(self):
        self.progress.active = True


dashboard = Dashboard()
pn.Column(dashboard.progress, pn.Param(dashboard.param.file_selector)).servable()

import panel as pn
import param


class Dashboard(param.Parameterized):
    file_selector = param.FileSelector()
    progress = pn.widgets.Progress(active=False)

    @param.depends("file_selector", watch=True)
    def activate_upload_status(self):
        self.progress.active = True


dashboard = Dashboard()
pn.Column(dashboard.progress, pn.Param(dashboard.param.file_selector)).servable()
