app.py

"""The FeatureInput enables a user to select from a list of features and set their values"""

import panel as pn
import param


class FeatureInput(pn.widgets.CompositeWidget):
    """The FeatureInput enables a user to select from a list of features and set their values

    ## Example

    ```python
    features = {
        "A": 1.0,
        "B": 2.0,
        "C": 3.0,
        "D": 4.0,
    }
    selected_features = ["A", "C"]
    widget = FeatureInput(features=features, selected_features=selected_features)
    ```
    """

    value = param.Dict(
        doc="The names of the features selected and their set values", allow_None=False
    )

    features = param.Dict(
        doc="The names of the available features and their default values",
        allow_None=False,
    )
    selected_features = param.ListSelector(
        doc="The list of selected features", allow_None=False
    )

    _selected_widgets = param.ClassSelector(
        class_=pn.Column, doc="The widgets used to edit the selected features"
    )

    _composite_type = pn.Column

    def __init__(self, **params):
        params["value"] = params.get("value", {})
        params["features"] = params.get("features", {})
        params["selected_features"] = params.get("selected_features", [])

        params["_selected_widgets"] = self.param._selected_widgets.class_()

        super().__init__(**params)

        selected_features_widget = pn.widgets.MultiChoice.from_param(
            self.param.selected_features, sizing_mode="stretch_width"
        )

        self._composite[:] = [selected_features_widget, self._selected_widgets]

    @param.depends("features", watch=True, on_init=True)
    def _reset_selected_features(self):
        selected_features = []
        for feature in self.selected_features.copy():
            if feature in self.features.copy():
                selected_features.append(feature)

        self.param.selected_features.objects = list(self.features)
        self.selected_features = selected_features

    @param.depends("selected_features", watch=True, on_init=True)
    def _handle_selected_features_change(self):
        org_value = self.value

        self._update_selected_widgets(org_value)
        self._update_value()

    def _update_value(self, *args):  # pylint: disable=unused-argument
        new_value = {}

        for widget in self._selected_widgets:
            new_value[widget.name] = widget.value

        self.value = new_value

    def _update_selected_widgets(self, org_value):
        new_widgets = {}

        for feature in self.selected_features:
            value = org_value.get(feature, self.features[feature])
            widget = self._new_widget(feature, value)
            new_widgets[feature] = widget

        self._selected_widgets[:] = list(new_widgets.values())

    def _new_widget(self, feature, value):
        widget = pn.widgets.FloatInput(
            name=feature, value=value, sizing_mode="stretch_width"
        )
        pn.bind(self._update_value, widget, watch=True)
        return widget


def create_app():
    features = {
        "Blade Length (m)": 73.5,
        "Cut-in Wind Speed (m/s)": 3.5,
        "Cut-out Wind Speed (m/s)": 25,
        "Grid Connection Capacity (MW)": 5,
        "Hub Height (m)": 100,
        "Rated Wind Speed (m/s)": 12,
        "Rotor Diameter (m)": 150,
        "Turbine Efficiency (%)": 45,
        "Water Depth (m)": 30,
        "Wind Speed (m/s)": 10,
    }
    selected_features = ["Wind Speed (m/s)", "Rotor Diameter (m)"]
    widget = FeatureInput(
        features=features,
        selected_features=selected_features,
        width=500,
    )

    return pn.FlexBox(
        pn.Column(
            "## Widget",
            widget,
        ),
        pn.Column(
            "## Value",
            pn.pane.JSON(widget.param.value, width=500, height=200),
        ),
    )


if pn.state.served:
    pn.extension(design="material")

    create_app().servable()