Dash error handling behavior

Hi, I’m wondering if this behavior is normal. When I run the following script, the error screen only show up the first time the app is loaded. After I refresh the page, the error screen doesn’t show up and the layout appears like there is no errors.


dash.exceptions.DuplicateIdError: Duplicate component id found in the initial layout: input_1

Traceback (most recent call last)

  • File “G:\Python\envs\testing2\Lib\site-packages\flask\app.py”, line 1515, in full_dispatch_request

rv = self.preprocess_request()

  • File “G:\Python\envs\testing2\Lib\site-packages\flask\app.py”, line 1857, in preprocess_request

rv = self.ensure_sync(before_func)()

  • File “G:\Python\envs\testing2\Lib\site-packages\dash\dash.py”, line 1307, in _setup_server

_validate.validate_layout(self.layout, self._layout_value())

  • File “G:\Python\envs\testing2\Lib\site-packages\dash_validate.py”, line 408, in validate_layout

raise exceptions.DuplicateIdError(

dash.exceptions.DuplicateIdError: Duplicate component id found in the initial layout: input_1

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Example script:

from dash import Dash,html
import dash_bootstrap_components as dbc

app = Dash(__name__,

app.layout = html.Div([
    dbc.Label("Input 1"),
    dbc.Label("Input 2"),
    dbc.Input(id='input_1'), #duplicated id

if __name__ == '__main__':

Environment: dash 2.7.0, dash_bootstrap_components 1.2.1

If it is normal, is there a way to change this behavior? I want to catch errors again even after I refresh the page to avoid missing error handling.

Troubleshooting Checklist
Verify that you can deploy an app in the App Catalog. These apps are supplied by Plotly and come with all the files required for deployment, which often allows you to eliminate app files as the cause of your issue.
Check that your app contains a Procfile and a requirements.txt (pip) or environment.yml (Conda). Learn more about required files.
Try running your app in a workspace.
Try deploying your app from a workspace. In Workspaces, Git and SSH are preconfigured, which often allows you to eliminate Git and SSH configurations as the cause of your issue.
Find the error message in your terminal, build logs, or app logs. Search for this error message on this page and follow the resolution steps.
Reach out to our support team with the error that you encountered.

This may help you,
Rachel Gomez

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