NoLayoutException: Layout must be a dash component or a function that returns a dash component

app = dash.Dash(__name__)

app.layout = html.Div([
                        dcc.Dropdown(id = 'demo-dropdown', 
                                     options = [{'label':str(item) , 'value':item } for item in df_copy['country_txt'].unique()],
             #dcc.Graph(id = 'Plot2', figure = fig2)
html.Div([dcc.Graph(id = 'id-graph', config = {'scrollZoom' : True})])

     Output('id-graph', 'figure'),
    [Input('demo-dropdown', 'value')])
def update_output(value):
    df_sub = df_copy.loc[df_copy['country_txt'] == value]
    #create graph
    location = [go.Scattermapbox(lon = df_sub['longitude'], lat = df_sub['latitude'] , mode = 'markers',hoverinfo= 'text' )]
    # return graph
    return {'data': location , 'layout':go.layout(uirevision = 'foo' , hovermode = 'closest' , hoverdistance = 2 , mapbox =dict(accesstoken = mapbox_access_token))}

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

Traceback Error:

NoLayoutException                         Traceback (most recent call last)
<ipython-input-42-705f648addcb> in <module>
      6                         dcc.Dropdown(id = 'demo-dropdown', 
      7                                      options = [{'label':str(item) , 'value':item } for item in df_copy['country_txt'].unique()],
----> 8                                      value = 'India'
      9                                     ),
     10              #dcc.Graph(id = 'Plot2', figure = fig2)

~\Anaconda3\envs\machine_learning\lib\site-packages\dash\ in layout(self, value)
    463     @layout.setter
    464     def layout(self, value):
--> 465         _validate.validate_layout_type(value)
    466         self._layout_is_function = isinstance(value, patch_collections_abc("Callable"))
    467         self._layout = value

~\Anaconda3\envs\machine_learning\lib\site-packages\dash\ in validate_layout_type(value)
    325     if not isinstance(value, (Component, patch_collections_abc("Callable"))):
    326         raise exceptions.NoLayoutException(
--> 327             "Layout must be a dash component "
    328             "or a function that returns a dash component."
    329         )

NoLayoutException: Layout must be a dash component or a function that returns a dash component.

I am not able to figure out how to deal with this. Even after removing the value and putting placeholder = ‘Select a country…’ , this gives same error at same line.

df_copy contains column country_txt which has country names.

Hi @matsujjudes and welcome to the Dash Community!

All of the layout components need to be contained within the app.layout.
Try making the layout like this:

app.layout = (
                    {"label": str(item), "value": item}
                    for item in df_copy["country_txt"].unique()
            # dcc.Graph(id = 'Plot2', figure = fig2)
            html.Div([dcc.Graph(id="id-graph", config={"scrollZoom": True})]),

It looks a lot different, but the only real change was moving ]), so the layout included the div with the graph.

It was reformatted using Black - which is a great tool, not only for making your code look nice (and PEP8 compliant) but it also makes it much easier to find bugs like this. (It’s saved me hours!)


Thanks…I didn’t know formatting a brackets would cause me so much trouble. I will surely try formatting extension.

this my code i have also the same message, please help me to solve it

# Import required libraries
import pandas as pd
import dash
from dash import html
from dash import dcc
from dash.dependencies import Input, Output, State
import plotly.graph_objects as go
import as px
from dash import no_update

# Create a dash application
app = dash.Dash(__name__)

# REVIEW1: Clear the layout and do not display exception till callback gets executed
app.config.suppress_callback_exceptions = True

# Read the airline data into pandas dataframe
airline_data =  pd.read_csv('', 
                            encoding = "ISO-8859-1",
                            dtype={'Div1Airport': str, 'Div1TailNum': str, 
                                   'Div2Airport': str, 'Div2TailNum': str})

# List of years 
year_list = [i for i in range(2005, 2021, 1)]

"""Compute graph data for creating yearly airline performance report 

Function that takes airline data as input and create 5 dataframes based on the grouping condition to be used for plottling charts and grphs.

    df: Filtered dataframe
   Dataframes to create graph. 
def compute_data_choice_1(df):
    # Cancellation Category Count
    bar_data = df.groupby(['Month','CancellationCode'])['Flights'].sum().reset_index()
    # Average flight time by reporting airline
    line_data = df.groupby(['Month','Reporting_Airline'])['AirTime'].mean().reset_index()
    # Diverted Airport Landings
    div_data = df[df['DivAirportLandings'] != 0.0]
    # Source state count
    map_data = df.groupby(['OriginState'])['Flights'].sum().reset_index()
    # Destination state count
    tree_data = df.groupby(['DestState', 'Reporting_Airline'])['Flights'].sum().reset_index()
    return bar_data, line_data, div_data, map_data, tree_data

"""Compute graph data for creating yearly airline delay report

This function takes in airline data and selected year as an input and performs computation for creating charts and plots.

    df: Input airline data.
    Computed average dataframes for carrier delay, weather delay, NAS delay, security delay, and late aircraft delay.
def compute_data_choice_2(df):
    # Compute delay averages
    avg_car = df.groupby(['Month','Reporting_Airline'])['CarrierDelay'].mean().reset_index()
    avg_weather = df.groupby(['Month','Reporting_Airline'])['WeatherDelay'].mean().reset_index()
    avg_NAS = df.groupby(['Month','Reporting_Airline'])['NASDelay'].mean().reset_index()
    avg_sec = df.groupby(['Month','Reporting_Airline'])['SecurityDelay'].mean().reset_index()
    avg_late = df.groupby(['Month','Reporting_Airline'])['LateAircraftDelay'].mean().reset_index()
    return avg_car, avg_weather, avg_NAS, avg_sec, avg_late

# Application layout
app.layout = html.Div(children=[ 
                                # TASK1: Add title to the dashboard
                                # Enter your code below. Make sure you have correct formatting.
                                html.H1('US Domestic Airline Flights Performance',style={'textAlign': 'center', 'color': '#503D36', 'font-size': 24}),
                                # REVIEW2: Dropdown creation
                                # Create an outer division 
                                    # Add an division
                                        # Create an division for adding dropdown helper text for report type
                                            html.H2('Report Type:', style={'margin-right': '2em'}),
                                        # TASK2: Add a dropdown
                                        # Enter your code below. Make sure you have correct formatting.
                                                                 {'label': 'Yearly Airline Performance Report', 'value': 'OPT1'},
                                                                 {'label': 'Yearly Airline Delay Report', 'value': 'OPT2'}
                                                         placeholder='Select a report type',
                                                         style={'width':'80%','padding':'3px','front size':'20px','text-align-last':'center'}
                                    # Place them next to each other using the division style
                                    ], style={'display':'flex'}),
                                   # Add next division 
                                       # Create an division for adding dropdown helper text for choosing year
                                            html.H2('Choose Year:', style={'margin-right': '2em'})
                                                     # Update dropdown values using list comphrehension
                                                     options=[{'label': i, 'value': i} for i in year_list],
                                                     placeholder="Select a year",
                                                     style={'width':'80%', 'padding':'3px', 'font-size': '20px', 'text-align-last' : 'center'}),
                                            # Place them next to each other using the division style
                                            ], style={'display': 'flex'}),  
                                # Add Computed graphs
                                # REVIEW3: Observe how we add an empty division and providing an id that will be updated during callback
                                html.Div([ ], id='plot1'),
                                        html.Div([ ], id='plot2'),
                                        html.Div([ ], id='plot3')
                                ], style={'display': 'flex'}),
                                # TASK3: Add a division with two empty divisions inside. See above disvision for example.
                                # Enter your code below. Make sure you have correct formatting.
                                        html.Div([], id='plot4'),
                                        html.Div([], id='plot5'),
                                ], style={'display':'flex'}),

# Callback function definition
# TASK4: Add 5 ouput components
# Enter your code below. Make sure you have correct formatting.
@app.callback([Output(component_id='plot1', component_property='children'),
               Output(component_id='plot2', component_property='children'),
               Output(component_id='plot3', component_property='children'),
               Output(component_id='plot4', component_property='children'),
               Output(component_id='plot5', component_property='children')
               Input(component_id='input-type', component_property='value'),
               Input(component_id='input-year', component_property='value'))
               # REVIEW4: Holding output state till user enters all the form information. In this case, it will be chart type and year
               [State("plot1", 'children'), State("plot2", "children"),
                State("plot3", "children"), State("plot4", "children"),
                State("plot5", "children")
# Add computation to callback function and return graph
def get_graph(chart, year, children1, children2, c3, c4, c5):
        # Select data
        df =  airline_data[airline_data['Year']==int(year)]
        if chart == 'OPT1':
            # Compute required information for creating graph from the data
            bar_data, line_data, div_data, map_data, tree_data = compute_data_choice_1(df)
            # Number of flights under different cancellation categories
            bar_fig =, x='Month', y='Flights', color='CancellationCode', title='Monthly Flight Cancellation')
            # TASK5: Average flight time by reporting airline
            # Enter your code below. Make sure you have correct formatting.
            line_fig= px.line(line_data, x='Month', y='AirTime', color='Reporting_Airline', title='Average monthly flight time (minutes) by airline')
            # Percentage of diverted airport landings per reporting airline
            pie_fig = px.pie(div_data, values='Flights', names='Reporting_Airline', title='% of flights by reporting airline')
            # REVIEW5: Number of flights flying from each state using choropleth
            map_fig = px.choropleth(map_data,  # Input data
                    hover_data=['OriginState', 'Flights'], 
                    locationmode = 'USA-states', # Set to plot as US States
                    range_color=[0, map_data['Flights'].max()]) 
                    title_text = 'Number of flights from origin state', 
                    geo_scope='usa') # Plot only the USA instead of globe
            # TASK6: Number of flights flying to each state from each reporting airline
            # Enter your code below. Make sure you have correct formatting.
            tree_fig = px.treemap(tree_data, path=['DestState', '...'], 
                                  title='Flight count by airline to destination state'
            # REVIEW6: Return dcc.Graph component to the empty division
            return [dcc.Graph(figure=tree_fig), 
            # REVIEW7: This covers chart type 2 and we have completed this exercise under Flight Delay Time Statistics Dashboard section
            # Compute required information for creating graph from the data
            avg_car, avg_weather, avg_NAS, avg_sec, avg_late = compute_data_choice_2(df)
            # Create graph
            carrier_fig = px.line(avg_car, x='Month', y='CarrierDelay', color='Reporting_Airline', title='Average carrrier delay time (minutes) by airline')
            weather_fig = px.line(avg_weather, x='Month', y='WeatherDelay', color='Reporting_Airline', title='Average weather delay time (minutes) by airline')
            nas_fig = px.line(avg_NAS, x='Month', y='NASDelay', color='Reporting_Airline', title='Average NAS delay time (minutes) by airline')
            sec_fig = px.line(avg_sec, x='Month', y='SecurityDelay', color='Reporting_Airline', title='Average security delay time (minutes) by airline')
            late_fig = px.line(avg_late, x='Month', y='LateAircraftDelay', color='Reporting_Airline', title='Average late aircraft delay time (minutes) by airline')

# Run the app
if __name__ == '__main__':

Hello @chrismubenga,

Welcome to the community!

What IDE are you using to work with the code?