# Pattern matching \`MATCH\` not working

**URL:** <https://community.plotly.com/t/pattern-matching-match-not-working/71681>\
**Category:** Dash Python\
**Tags:** question\
**Created:** [January 16, 2023, 11:32pm UTC](https://community.plotly.com/t/pattern-matching-match-not-working/71681 "2023-01-16T23:32:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Turing](https://avatars.discourse-cdn.com/v4/letter/t/e68b1a/32.png) [@Turing](https://community.plotly.com/u/Turing)\
**Post date:** [January 16, 2023, 11:32pm UTC](https://community.plotly.com/t/pattern-matching-match-not-working/71681/1 "2023-01-16T23:32:17Z")

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Hey everyone,

I am having trouble to get pattern matching with `MATCH` working. My dash app has a list of buttons that gets dynamically updated after a file is uploaded. When pressing a button I want to read a specific file associated with a single button. For this I was trying to use pattern matching with `MATCH` in order to read the id of the pressed button. However this prevents my callback from being executed. Using `ALL` somehow works but with this I am not able to know which button was pressed. My app looks something like this:

```auto
app = Dash( __name__ )

app.layout = html.Div(
    children=[
        html.Div(
            children=[
                html.Button(file, id={'type': 'saved-button', 'index': f'{file}'}) for file in files
            ],
            id='file_list'),

        dcc.Graph(
            id='fig'
            figure=fig
        ),

        dcc.Upload(
            id='upload-data'
        )
    ]
)

@app.callback(
        [Output('fig', 'figure'), Output('file_list', 'children')],
        [Input('upload-data', 'contents'), Input('upload-data', 'filename'), Input({'type': 'saved-button', 'index': ALL}, 'n_clicks')],
        [State('file_list', 'children'), State({'type': 'saved-button', 'index': MATCH}, 'id')],
        prevent_initial_call=True
    )
    def process(contents, filename, n_clicks, children, button_id):
        # Check if button was pressed or a file was uploaded
        if ctx.triggered_id != 'upload-data':
            file = f'{button_id["index"]}.parquet'
            data = pd.read_parquet(file)

            # Some processing and plotting fig

            return [fig, children]

        # Some processing in case a file was uploaded and creating fig

        # Saving data to disk and creating new button
        filename = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
        df.to_parquet(f'{filename}.parquet')
        new_item = html.Button(
            filename,
            id={
                'type': 'saved-button',
                'index': filename
            }
        )

        children.append(new_item)

        return [fig, children]

```

Basically I am having problems with this piece of code: `State({'type': 'saved-button', 'index': MATCH}, 'id')`. When `MATCH` is replaced with all `ALL` at least the callback gets executed (although not with the intended logic). Thankful for any help and hints you might have 🙂

---

<div class="post-metadata">

**Author:** ![jinnyzor](https://sea2.discourse-cdn.com/flex024/user_avatar/community.plotly.com/jinnyzor/32/21194_2.png) [@jinnyzor](https://community.plotly.com/u/jinnyzor)\
**Post date:** [January 17, 2023, 1:03am UTC](https://community.plotly.com/t/pattern-matching-match-not-working/71681/2 "2023-01-17T01:03:55Z")

</div>

Hello @Turing,

Using ALL is the way to go, since your output target is always the same.

The easiest way to know which button was pushed is `ctx.triggered_id.index` with pattern-matching. 😁