Demo of the dropdown's value not being reset when it is removed from the list of options.

dropdown-value-not-reset.py

import dash
import dash_core_components as dcc
import dash_html_components as html
from dash.dependencies import Input, Output, State
from dash.exceptions import PreventUpdate
from flask import Flask, send_file

server = Flask(__name__)
app = dash.Dash(server=server)


app.layout = html.Div(
    children=[
        dcc.Store(id="jobs", storage_type="memory"),
        html.H1("Jobs"),
        html.Div(id="jobs-list"),
        html.H2("Upload your files"),
        dcc.Upload(
            id="upload-data",
            children=html.Div(
                ["Drag and drop or click to select a file to upload."]
            ),
            style={
                # "width": "100%",
                "height": "60px",
                "lineHeight": "60px",
                "borderWidth": "1px",
                "borderStyle": "dashed",
                "borderRadius": "5px",
                "textAlign": "center",
                "margin": "10px",
            },
            multiple=True,
        ),
        html.H2("Delete jobs"),
        dcc.Dropdown(id="jobs-to-delete", multi=True),
        html.Button("Delete Me!", id="delete-jobs-button", n_clicks=0),
        html.H2("Select a job for detailed display"),
        dcc.Dropdown(id="current-job"),
        html.H2("Jobs Details"),
        html.Div(id="current-job-details"),
    ],
    style={"max-width": "500px"},
)


@app.callback(
    Output("jobs-list", "children"), [Input("jobs", "data")],
)
def display_jobs(jobs):
    return [html.Div(f"Job: {j}") for j in jobs]


@app.callback(
    Output("jobs", "data"),
    [
        Input("upload-data", "filename"),
        Input("delete-jobs-button", "n_clicks"),
    ],
    [State("jobs-to-delete", "value"), State("jobs", "data")],
)
def update_jobs(new_jobs, button, delible_jobs, jobs):
    if new_jobs is None and delible_jobs is None:
        raise PreventUpdate

    triggers = dash.callback_context.triggered
    jobs = jobs or []

    butt_prop = "delete-jobs-button.n_clicks"
    if any([t["prop_id"] == butt_prop for t in triggers]):
        jobs = [j for j in jobs if j not in delible_jobs]

    up_prop = "upload-data.filename"
    if any([t["prop_id"] == up_prop for t in triggers]):
        jobs += new_jobs

    return jobs


@app.callback(
    [Output("current-job", "options"), Output("jobs-to-delete", "options")],
    [Input("jobs", "data")],
)
def update_selectable_jobs(jobs):
    if jobs is None:
        raise PreventUpdate

    options = [{"label": f"Job: {j}", "value": j} for j in jobs]
    return [options, options]


@app.callback(
    Output("current-job-details", "children"),
    # FIXES_IT [Input("current-job", "value"), Input("current-job", "options"),],
    [Input("current-job", "value"), Input("current-job", "options"),],
    [State("current-job-details", "children")],
)
# FIXES_IT def display_current_job(job_id, options, divs):
def display_current_job(job_id, options, divs):
    print(f"DISPLAY: {job_id} -> {options}")
    # There's nothing to do.
    if job_id is None and divs is None:
        raise PreventUpdate

    # There's no current selection but there's something being
    # displayed, so clear the display.
    if job_id is None:
        return []

    # FIXES_IT if all([job_id != o["value"] for o in options]):
    # FIXES_IT    return []

    divs = []
    divs.append(html.Div(children=[f"Detailed explanation of {job_id}"]))

    return divs


if __name__ == "__main__":
    app.run_server(debug=True, port=8888, host="172.16.193.97")