# Duplicate call back

**URL:** <https://community.plotly.com/t/duplicate-call-back/23342>\
**Category:** Dash Python\
**Created:** [May 11, 2019, 11:56am UTC](https://community.plotly.com/t/duplicate-call-back/23342 "2019-05-11T11:56:46Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Jason4](https://avatars.discourse-cdn.com/v4/letter/j/a5b964/32.png) [@Jason4](https://community.plotly.com/u/Jason4)\
**Post date:** [May 11, 2019, 11:56am UTC](https://community.plotly.com/t/duplicate-call-back/23342/1 "2019-05-11T11:56:46Z")

</div>

Hi. I am stuck with a Duplicate callback error and i dont know how to get around it.

I am using a drop down to filter which data depending on zones. Can anyone help with a solution.

html.Div([  
html.Div([  
html.Label(‘SELECT YOUR REGION’),  
dcc. Dropdown(id=‘chooseregion’,  
options=[  
{‘label’: ‘EUR’, ‘value’: ‘EUR’},  
{‘label’: ‘AFRICA’, ‘value’: ‘AF’},  
{‘label’: ‘ASIA’, ‘value’: ‘AS’},  
{‘label’:‘N.AMERICA’,‘value’:‘NA’}

my callback:

@app.callback(  
Output(‘Bar\_graph’,‘figure’),  
[Input(‘chooseregion’,‘value’)])

def update\_graph(region\_chosen):  
filtered\_df=Pivot\_Month[Pivot\_Month[‘Region’]==region\_chosen]  
data=[]  
for i in filtered\_df.Region.unique():  
Pivot\_by\_zone = Pivot\_Month[Pivot\_Month[‘Region’]==i]  
traces.append(go.Bar(  
x=Pivot\_Month[‘Region’],  
y=Pivot\_Month[‘Amount’],  
text=Pivot\_Month[‘Region’]))  
figure={  
‘data’:data,  
‘layout’: {  
‘title’:‘Data Vizualization’

My error message:

DuplicateCallbackOutput:  
You have already assigned a callback to the output  
with ID “Bar\_graph” and property “figure”. An output can only have  
a single callback function. Try combining your inputs and  
callback functions together into one function.

---

<div class="post-metadata">

**Author:** ![Jobo](https://avatars.discourse-cdn.com/v4/letter/j/ce7236/32.png) [@Jobo](https://community.plotly.com/u/Jobo)\
**Post date:** [August 21, 2019, 9:21am UTC](https://community.plotly.com/t/duplicate-call-back/23342/2 "2019-08-21T09:21:17Z")

</div>

I have a similar issue.