multiple inputs in plotly dash error: 'Lenths match'

Question

I have three inputs for my map in the plotly dash and I want to use px.scatter_mapbox as the map type. Meanwhile, the data has three categorical columns, including 'region', 'country' and 'status', with one metric column of '4/24/20'. These three dimensions are multiple dropdown which I think they have no problem (normal to show up). The problem is the callback below. It is always showing the error of 'Lengths must compare to match'. I am totally lost.

@app.callback(
    Output('map-graph', 'figure'),
    [Input('region_dropdown_id', 'value'),
     Input('country_dropdown_id', 'value'),
     Input('status_dropdown_id', 'value')
     ],
)
def map_selection(input1, input2, input3):
    import plotly.express as px
    MBToken = 'your token'
    px.set_mapbox_access_token(MBToken)
    dff = df
    dff = dff[dff["4/24/20"]>0]
    filtered_df = dff[(dff['region'] == input1) & (dff['country'] == input2) & (dff['status'] == input3)]
    fig = px.scatter_mapbox(filtered_df, lat="Lat", lon="Long",     color= input3, size="4/24/20",
                      color_continuous_scale=px.colors.cyclical.IceFire, size_max=100, zoom=0)
    return fig

Swazy · Accepted Answer · 2020-04-25 15:18:41Z

1

It looks like you are using multi-value dropdown Dash components so their 'value' attributes are actually Python lists rather than individual values.

The following modification to your code should hopefully fix the error:

filtered_df = dff[(dff['region'] == input1[0]) & (dff['country'] == input2[0]) & (dff['status'] == input3[0])]

But this obviously assumes you will only ever be selecting one value in the multi-value dropdowns. If that is your intention you might consider changing these to a different type of dropdown. They are all listed here. Hope that helps!

edited Apr 25, 2020 at 15:18

answered Apr 25, 2020 at 15:08

Swazy

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