Browser shows 'Error loading dependencies'. No other errors

Dash Python
1

The following gives only an Error loading dependencies message in the browser window. I don’t get any error messages elsewhere, and I’m not sure what is causing the error.

If I comment out lines 135 - 149 and uncomment lines 121 - 132 then the app runs correctly.

import dash
import dash_table
from dash.dependencies import Input, Output
import dash_core_components as dcc
import dash_html_components as html

equals = ' = '
plus = ' + '
end = ''

apples={
            'name': 'apples',
            'val': '10',
            'rel': '2'
           }

bananas={
            'name': 'bananas',
            'val': '10',
            'rel': '2'
           }

pears={
            'name': 'pears',
            'val': '10',
            'rel': '2'
           }

oranges={
            'name': 'oranges',
            'val': '10',
            'rel': '2'
           }

kiwi={
            'name': 'kiwi',
            'val': '10',
            'rel': '2'
           }

all_metrics = {
    'apples_list' : {'items': [apples, pears, bananas], 'operators': [equals, plus, end]},
    'bananas_list' : {'items': [bananas, oranges, apples, kiwi], 'operators': [equals, plus, plus, end]},
    'kiwi_list': {'items': [kiwi, apples, bananas], 'operators': [equals, plus, end]},
    'pears_list': {'items': [pears, bananas, kiwi, oranges], 'operators': [equals, plus, plus, end]},
    'oranges_list': {'items': [oranges, apples, bananas], 'operators': [equals, plus, end]}
              }

current_metric = all_metrics['apples_list']

all_items = list(set([
                    item['name']
                        for each in all_metrics.keys()
                            for item in all_metrics[each]['items']
                ]))

def component(name, val, rel):
    return html.Div(
            id=name+'_div',
            children=[dash_table.DataTable(
                        id=name,
                        columns=[
                            {"name": [name, 'abs'], "id": 'abs'},
                            {"name": [name, 'rel'], "id": 'rel'},
                        ],
                        data=[
                            {
                                "abs": val,
                                "rel": rel,
                            }
                        ],
                        style_table= {'maxWidth': '200'},
                        merge_duplicate_headers=True,
                    )
            ], style={'width':'120px'})


def combine_components(relationship):
    relationship = relationship['items'][0]['name'] + '_list'
    return html.Div(
            children=[
            val for pair in zip(
                    [
                    component(each['name'], each['val'], each['rel'])
                    for each in all_metrics[relationship]['items']
                    ],
                    all_metrics[relationship]['operators']
                   )
                    for val in pair
                    ],
                style={'display': 'flex', 'flex-direction': 'row'}
           )


app = dash.Dash(__name__)

# create callbacks for a component which is not yet in the layout
app.config.supress_callback_exceptions = True

app.layout = html.Div([
                html.Div([
                    dcc.Dropdown(
                        id='dropdown',
                        options=[
                            {'label': j, 'value': j} for j in all_items
                        ],
                        value=current_metric['items'][0]['name'],
                        style={'width':'120px', 'margin-bottom':'10px'},
                        searchable=True,
                        clearable=False
                    ),
                    html.Div(
                        id='canvas',
                        children=combine_components(current_metric),
                        style={}
                    )
                ])
            ])


#  @app.callback(
    #  Output('canvas', 'children'),
    #  [Input('dropdown', 'value')]
#  )
#  def update_metrics(value):
    #  relationship=str(value)+'_list'
#
    #  print(all_metrics[relationship]['items'])
#
    #  print([ Input(item['name'], 'n_clicks') for item in all_metrics[relationship]['items'] ])
#
    #  return combine_components(all_metrics[relationship])


@app.callback(Output('canvas', 'children'),
             [Input(item+'_div', 'n_clicks') for item in all_items])
def update_metrics(*all_items):
    ctx = dash.callback_context

    if not ctx.triggered:
        msg = 'None of the buttons have been clicked yet'
    else:
        clicked = ctx.triggered[0]['prop_id'].split('.')[0].split('-')[1]
        print(f'clicked: {clicked}')
        msg = f'Button {clicked} was most recently clicked'

    value=clicked
    relationship=str(value)+'_list'
    return combine_components(all_metrics[relationship])




if __name__ == '__main__':
    app.run_server(debug=True)