# User guide's multipage demo breaks

**URL:** <https://community.plotly.com/t/user-guides-multipage-demo-breaks/6772>\
**Category:** Dash Python\
**Created:** [November 13, 2017, 11:27am UTC](https://community.plotly.com/t/user-guides-multipage-demo-breaks/6772 "2017-11-13T11:27:12Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![chrisalbon](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/chrisalbon/32/2086_2.png) [@chrisalbon](https://community.plotly.com/u/chrisalbon)\
**Post date:** [November 13, 2017, 11:27am UTC](https://community.plotly.com/t/user-guides-multipage-demo-breaks/6772/1 "2017-11-13T11:27:12Z")

</div>

I was having some strange errors trying to make a multipage dashboard, so I replicated the demo app at the bottom of the [multipage documentation](https://plot.ly/dash/urls) page.

However, running [index.py](http://index.py) gave me an error:

```
Traceback (most recent call last):
  File "index.py", line 6, in <module>
    from apps import app1, app2
  File "XXXXX/app/apps/app2.py", line 24, in <module>
    [Input('app-1-dropdown', 'value')])
  File "XXXXX/anaconda3/lib/python3.6/site-packages/dash/dash.p", line 485, in callback
    self._validate_callback(output, inputs, state, events)
  File "XXXXX/anaconda3/lib/python3.6/site-packages/dash/dash.py", line 471, in _validate_callback
    output.component_property).replace(' ', ''))
dash.exceptions.CantHaveMultipleOutputs:
You have already assigned a callback to the output
with ID "app-1-display-value" and property "children". An output can only have
a single callback function. Try combining your inputs and
callback functions together into one function.

```

For the life of me, I can’t backtrace the solution. Any help appreciated.

---

<div class="post-metadata">

**Author:** ![chrisalbon](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/chrisalbon/32/2086_2.png) [@chrisalbon](https://community.plotly.com/u/chrisalbon)\
**Post date:** [November 13, 2017, 11:31am UTC](https://community.plotly.com/t/user-guides-multipage-demo-breaks/6772/2 "2017-11-13T11:31:05Z")

</div>

Nevermind, as always in the act of posting I figured out the issue. [app2.py](http://app2.py) needed to have its values changed from “app-1” etc to “app-2”