A nonexistent object was used in an `Output` of a Dash callback.?

Dash Python
17

Sure, hope the below works:

app.py

import dash
from dash import html, dcc
import dash_bootstrap_components as dbc
from datetime import datetime as dt

# default bootstrap theme
app = dash.Dash(__name__, use_pages=True, external_stylesheets=[dbc.themes.BOOTSTRAP], suppress_callback_exceptions=True)

#sidebar
SIDEBAR_STYLE = {
    "position": "fixed",
    "top": 0,
    "left": 0,
    "bottom": 0,
    "width": "16rem",
    "padding": "2rem 1rem",
    "color": "#7F7F7F",
    "background-color": "#EBEBEB"}

# the styles for the main content position it to the right of the sidebar and
# add some padding.
CONTENT_STYLE = {
    "margin-left": "18rem",
    "margin-right": "2rem",
    "padding": "2rem 1rem",}

sidebar = html.Div(
    [
        html.Hr(),
        dbc.Nav(
            [
                dbc.NavLink("Home", href="/", active="exact"),
                dbc.NavLink("Pages 1", href="/pages_1", active="exact")
            ],
            vertical=True,
            pills=True,
        ),
    ],
    style=SIDEBAR_STYLE,
)

navbar = dbc.Navbar()

# content from pages
content = html.Div(dash.page_container, style=CONTENT_STYLE)

app.layout = html.Div([
    sidebar, navbar,
    dcc.Location(id="url"),
    dcc.Loading(id='load',
                type='default',
                children=[
                    html.Div([dcc.Store(id='data_memory'),
                              dcc.Store(id='ccy_memory')])
                ], fullscreen=True),
    dbc.Col(
        html.Div(html.H3('My App:', style={'fontSize': 20}),
                 style={'margin-top': '10px','padding-left': '130px'}),
        width={'size': 6, 'offset': 1}),

    dbc.Row([
        dbc.Col(html.Div(dcc.DatePickerSingle(id='date_picker',
                                              max_date_allowed=dt.date(dt.today()),
                                              initial_visible_month=dt.date(dt.today()),
                                              display_format='MMM Do, YY',
                                              placeholder='Select date',
                                              persistence=True,
                                              persistence_type='session',
                                              persisted_props=['date'],

                                              style={'margin-bottom': '10px','padding-left': '130px'})),
                width={'size': 1, 'offset': 1}),
        dbc.Col(html.Div(
            dbc.Button("Refresh Trades", id="button_eur", className="me-1"), style={'margin-top': '6px'}),
            width={'size': 2, 'offset': 1})
    ]
    ), content])



if __name__ == "__main__":
    app.run(debug=True)

pages_1.py

import dash
from dash import dcc, html, callback
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output, State
from dash.exceptions import PreventUpdate
import plotly_express as px
import pandas as pd

dash.register_page(
    __name__,
    path='/pages_1',
    title='Page 1',
    name='Page 1'
)

layout = html.Div([
    html.Hr(),
    html.H3("Page 1"),
    dbc.Row(
        dbc.Col(
            html.Div(html.H3('DropDown Below:', style={'fontSize': 20}),
                     style={'padding-left': '10px', 'margin-top': '20px'}),
            width={'size': 6})),

    # File selection dropdown
    dbc.Row(
        dbc.Col(
            html.Div(dcc.Dropdown(id='ccy_dropdown',
                                  multi=False,
                                  placeholder='Select currency'),
                     style={'padding-left': '10px'}),
            width={'size': 2})),
    dbc.Row(
        dbc.Col(
            html.Div(dcc.Dropdown(id='fund_dropdown',
                                  multi=False,
                                  placeholder='Select fund',
                                  options=[{'label': c, 'value': c} for c in ['One', 'Two']],
                                  value='One'),
                     style={'padding-left': '10px'}),
            width={'size': 2})),

    dbc.Row(
        dbc.Col(
            html.Div(
                dcc.Graph(id='fx_points_fig', style={'width': '95vh', 'height': '95vh'}
                          ),
                style={'margin-top': '50px', 'width': '95%'}
            )
        )
    )
]
)

@callback([Output('data_memory', 'data'), Output('ccy_dropdown', 'options')],
          [Input('button_eur', 'n_clicks'), State('date_picker', 'date')], prevent_initial_call=True) 
def update_latest_trades(but, date_value):
    if date_value is None or but is None:
        raise PreventUpdate

    try:

         datasets = {'data': 3}
         dd_options = [{'label': c, 'value': c} for c in ['One','Two']]

         return datasets, dd_options

    except:
        return None, None

@callback(Output('fx_points_fig', 'figure'),
          [Input('ccy_dropdown', 'value'), Input('button_eur', 'n_clicks'),
          Input('fund_dropdown', 'value'), State('data_memory', 'data')],prevent_initial_call=True)
def generate_fx_points_table(ccy, n, fund, data):
    if ccy is None:
        raise PreventUpdate

    df = pd.DaraFrame(data=[['One',2,3],['Two',4,5]], columns = ['Fund','Currency','Points'])

    fig = px.scatter(df.loc[df['Fund'].isin([fund])], x='Currency', y="Points")

    return fig

Tried to make the example as min as possible, thanks a lot for your help here. The app was working before I tried using the dash pages. Looks like there was a similar discussion here but no solution: 📣 Dash v1.11.0 Release - Introducing Pattern-Matching Callbacks - #2 by chriddyp