# Callback call other callbacks

**URL:** <https://community.plotly.com/t/callback-call-other-callbacks/31516>\
**Category:** Dash Python\
**Created:** [November 18, 2019, 6:23pm UTC](https://community.plotly.com/t/callback-call-other-callbacks/31516 "2019-11-18T18:23:38Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![JoseMarqueses](https://avatars.discourse-cdn.com/v4/letter/j/838e76/32.png) [@JoseMarqueses](https://community.plotly.com/u/JoseMarqueses)\
**Post date:** [November 18, 2019, 6:23pm UTC](https://community.plotly.com/t/callback-call-other-callbacks/31516/1 "2019-11-18T18:23:38Z")

</div>

Hi,

I have two sliders inside a html.Div. when i change the children of the Div, it fire a callback which have a slider as input, why. This is the example code:

```auto
import dash
import dash_html_components as html
import dash_core_components as dcc
import dash_bootstrap_components as dbc

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash( __name__ , external_stylesheets=external_stylesheets)
app.config.suppress_callback_exceptions=True

app.layout = html.Div([
                dbc.Button("Add slider",id="button"),
                html.Div([
                    
                ],id='range-sliders'),
                html.Div(id='output-container-range-slider')
            ])

@app.callback(
    Output('range-sliders','children'),
    [Input('button','n_clicks')],
    [State('range-sliders','children')]
)
def addslider(click,children):
    print("2")
    if children:
        if click:
            children[0]['props']['value'] = [0,20]
            return children
        
    else:
        children.append(html.Div([
                dcc.RangeSlider(
                    id='range1',
                    min=0,
                    max=20,
                    step=0.5,
                    value=[5, 15]
                ),
                    dcc.RangeSlider(
                    id='range2',
                    min=0,
                    max=20,
                    step=0.5,
                    value=[5, 15]
                )]))
    return children

@app.callback(
    dash.dependencies.Output('output-container-range-slider', 'children'),
    [dash.dependencies.Input('range1', 'value')])
def update_output(value):
    print("1")
    return 'You have selected "{}"'.format(value)

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

```

Note: when I click in button, the ouput show:  
2  
1  
2  
1  
2  
1

---

<div class="post-metadata">

**Author:** ![JoseMarqueses](https://avatars.discourse-cdn.com/v4/letter/j/838e76/32.png) [@JoseMarqueses](https://community.plotly.com/u/JoseMarqueses)\
**Post date:** [November 18, 2019, 9:03pm UTC](https://community.plotly.com/t/callback-call-other-callbacks/31516/2 "2019-11-18T21:03:41Z")

</div>

nobody? I would like modify the children without call the other callback

---

<div class="post-metadata">

**Author:** ![Hammad](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/hammad/32/8518_2.png) [@Hammad](https://community.plotly.com/u/Hammad)\
**Post date:** [November 19, 2019, 12:05am UTC](https://community.plotly.com/t/callback-call-other-callbacks/31516/3 "2019-11-19T00:05:45Z")

</div>

Hey @JoseMarqueses,

You can use “callback context” in order to fire the callback when a specific property is triggered. It uses the global variable `dash.callback_context` which is available in callbacks to access the list of changed properties within a callback. You can learn more about it in the Dash documentation FAQs [here](https://dash.plot.ly/faqs).

I’ve modified your code below to use callback context to only fire the children after you press the button, I think that’s what your post above is looking for. Let me know if that’s on point. Cheers.

```python

import dash
import dash_html_components as html
import dash_core_components as dcc
import dash_bootstrap_components as dbc
from dash.dependencies import Input, Output, State
import pdb

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash( __name__ , external_stylesheets=external_stylesheets)
app.config.suppress_callback_exceptions = True

app.layout = html.Div([
    html.Div(id='test'),
    dbc.Button("Add slider", id="button"),
    html.Div([

    ], id='range-sliders'),
    html.Div(id='output-container-range-slider')
])

@app.callback(
    Output('range-sliders', 'children'),
    [Input('button', 'n_clicks')],
    [State('range-sliders', 'children')]
)
def addslider(click, children):
    print("2")
    if children:
        if click:
            children[0]['props']['value'] = [0, 20]
            return children

    else:
        children.append(html.Div([
            dcc.RangeSlider(
                id='range1',
                min=0,
                max=20,
                step=0.5,
                value=[5, 15]
            ),
            dcc.RangeSlider(
                id='range2',
                min=0,
                max=20,
                step=0.5,
                value=[5, 15]
            )]))
    return children

@app.callback(
    Output("output-container-range-slider", "children"),
    [Input("button", "n_clicks"),
     Input("range-sliders", "children")],

)
def update_output(clicks, value):
    print("1")
    ctx = dash.callback_context
    if "range-sliders.children" in ctx.triggered[0]['prop_id']:
        return 'You have selected "{}"'.format(value[0]['props']['children'][0]['props']['value'])

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

```

---

<div class="post-metadata">

**Author:** ![JoseMarqueses](https://avatars.discourse-cdn.com/v4/letter/j/838e76/32.png) [@JoseMarqueses](https://community.plotly.com/u/JoseMarqueses)\
**Post date:** [November 19, 2019, 10:08am UTC](https://community.plotly.com/t/callback-call-other-callbacks/31516/4 "2019-11-19T10:08:21Z")

</div>

and this case?

```auto
import dash
from dash.dependencies import Input, Output, State
import dash_html_components as html
import dash_core_components as dcc
import ast

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash( __name__ , external_stylesheets=external_stylesheets)
app.config.suppress_callback_exceptions=True

app.layout = html.Div([
    html.Button('Add a slider', id='button', n_clicks=0),
    html.Div(children=[],id='slider-container'),
    # this is a hack: include a hidden dcc component so that
    # dash registers and serve's this component's JS and CSS
    # libraries
    dcc.Input(style={'display': 'none'})
])

@app.callback(
    Output('slider-container', 'children'),
    [Input('button', 'n_clicks')],
    [State('slider-container','children')])
def add_sliders(n_clicks,children):
    print("1")
    #global children
    if children:
        if n_clicks:
            print(children)
        return children
    else:
        for i in range(10):
            children.append(html.Div(
                [html.Div([
                html.Div(dcc.RangeSlider(
                    id='slider-{}'.format(i),
                    min=0,
                    max=20,
                    step=0.5,
                    value=[5, 15]
                ),),
                html.Label(id='output-{}'.format(i), style={'marginTop': 30})
            ])]
            ))
        return children

def generate_input():
    c = [Input('slider-{}'.format(i), 'value') for i in range(10)]
    return tuple(c)

def generate_output():
    c = [Output('output-{}'.format(i), 'children') for i in range(10)]
    return tuple(c)

@app.callback(
    [a for a in generate_output()],
    [a for a in generate_input()])
def update_output(*slider_i_value):
    print("2")
    ctx = dash.callback_context
    if ctx.triggered:
        print(ctx.triggered)
        print("3")
        return slider_i_value

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

```

When you start app, Update\_output is called and if you change a value of a range-slider Update\_output save the last call and is called twice. This is an example but i need this for a proyect. And it’s possible return only a value when you have more than one outputs? and return value to specific Output.

Thank!