How to write into a PointDraw stream?

HoloViews
,
1

I need to have sync between a hv.Points plot and a DataFrame, while enabling a PointDraw tool. Yes, this calls for an Annotator, but I don’t know how to extend Annotator with further callbacks.
So, I tried the following approach, where I am using PointDraw for do plot->df sync, and a separate text box to do the renaming of annotations. And… it almost works. I just need a pointer how to let the points_stream know the vdim has changed.

import param
import pandas as pd

import panel as pn
pn.extension('tabulator')
import holoviews as hv
hv.extension('bokeh')

import logging
logger = logging.getLogger()
logger.setLevel(logging.DEBUG)

_coords_column_order = ['site','x', 'y']

class SG(param.Parameterized):

    coords = param.DataFrame(columns=_coords_column_order,doc="Dataframe containing coordinates",)
    plot = param.ClassSelector(class_=hv.Points)
    points_stream = param.ClassSelector(class_=hv.streams.PointDraw,)
    sel_stream = param.ClassSelector(class_=hv.streams.Selection1D,default=hv.streams.Selection1D())


    def plot_points(self, coords=None):
        if coords is None:
            coords = self.coords
        plot = hv.Points(coords, kdims=['x','y'], vdims=['site'])
        plot.opts(size=10,tools=['hover'],active_tools = ['point_draw',"wheel_zoom"])
        return plot

    def __init__(self,coords):

        plot = self.plot_points(coords)
        ps = hv.streams.PointDraw(data=plot.columns(), source=plot, empty_value='')
        ss = hv.streams.Selection1D(source=plot)

        super().__init__(
            coords = coords,
            points_stream = ps,
            plot = plot,
            sel_stream = ss
        )


    @pn.depends("points_stream.data", watch=True)
    def _update_coordinates_from_plot(self):
        self.coords = pd.DataFrame(self.points_stream.data)[_coords_column_order]

    def rename_site(self, new_site_name):
        logger.debug("=======\ntrying to rename site with index")
        i = self.sel_stream.index
        logger.debug(f"i: {i}, new name: {new_site_name}")
        df = self.coords.copy()
        df.loc[i,'site'] = new_site_name
        self.coords = df

coords = pd.DataFrame(
    { "site":list("ABC"), "x":[0,.2,.4], "y":[0,.1,0]},
)
A = SG(coords)
rename_text = pn.widgets.TextInput(width=100)
def rename(event):
    A.rename_site(event.new)
    logger.debug("\n"+str(A.coords))
rename_text.param.watch(rename, "value")

tbl_view = pn.widgets.Tabulator.from_param(
    A.param.coords,
    show_index=False,
)
text = "To rename a site, select it on a plot by clicking, then enter the new name in the text box below, and confirm by pressing enter."
main = pn.Row(
    pn.Column(tbl_view,text,rename_text),
    A.plot
)
main.servable()

Right now, the renaming is registered at the level of the main dataframe, but the points_stream does not know about it. So, the next time, the renamed point is being dragged, the dataframe’s 'site' reverts back to what it was before renaming.

2

Ok, I’ve figured this one out: I can trigger the update to the stream using the event method. Essentially using self.points_stream.event(data = df.to_dict()) as the last line in rename_site.

Unfortunately, this did not help me in the end, as I’ve discovered that updating the stream does not reflect in the stream’s source plot. So, I guess I need to change the question into “How to update hv.Points’ data programmatically?”.

I’ve tried self.points_stream.source.data = df.to_dict() and self.plot.data = df.to_dict() in the rename_site with no luck. These did not throw any errors though…