plotly / plotly/dash

Dash 2.0 DataTable Previous Data Loses Column Order

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bug dash-data-table P3
Dominant language
Python
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Description

In dash v1.19.0 with dash-table v4.11.2 the data_previous property of a DataTable retained the order of the columns
In dash v2.0.0 this property now returns the columns ordered alphabetically; not based on previous ordering

Minimal reproducible example:

from dash import Dash, Input, Output, State
from dash.exceptions import PreventUpdate
from dash.html import Div, Button
from dash.dash_table import DataTable
from pandas import DataFrame

df = DataFrame(dict(Z=[1, 2, 3], A=[7, 8, 9], L=[4, 5, 6]))
app = Dash(__name__)
table = DataTable(id='table', columns=[dict(name=i, id=i, deletable=True) for i in df.columns],
                  data=df.to_dict('records'))
undo_button = Button(id='undo-button', children='Undo')
app.layout = Div([Div(table), Div(undo_button)])


@app.callback([Output(table.id, 'columns'), Output(table.id, 'data')],
              Input(undo_button.id, 'n_clicks'),
              State(table.id, 'data_previous'))
def undo(n_clicks, previous_data):
    if n_clicks is None:
        raise PreventUpdate
    df = DataFrame(previous_data)
    return [dict(name=i, id=i, deletable=True) for i in df.columns], df.to_dict('records')

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

If I delete any of these columns, and then click the undo button, I expect the deleted column to be restored, and the order of the columns to remain Z, A, L

Initial table:
image

Deleted column:
image

Following undo:
image

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Run the minimal reproducible example with the stated Dash and dash-table versions, focusing on DataTable's data_previous property after deleting a column. Compare the returned record order between versions and verify that restoring the deleted column preserves the original Z, A, L order.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
data-visualization, frontend
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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