Editable Data Table: How to give a cell a default value if the user hits backspace instead of an empty cell?

Dash Python
1

So currently when you hit backspace in an editable Data Table, the cell is just going to be empty.
I want to fill the cell automatically with a default value (for example 0).

Now one way to achieve this is maybe to make a callback that has ‘data’ or the timestamp as input and always compare the full table content with the state it was previously in.
But in my case I have a pretty big table and firing a callback and transfering the whole data content over the network whenever a user hits backspace to delete a value seems super inefficient.

It would be really neat if there was a function such as those style conditionals, but for more than just styling…

Does anyone has an idea how to implement such a thing or is this currently not possible?

1 Like
2

@dimark Good question!

There is a mechanism that coerces & validates data entry in the table but it is not applied when deleting the cells with backspace with either a single or multiple cells selected.

Also just found out that the 0 number default case is not applied correctly because is it falsy and the validation contains a bug.

Opened an issue and a PR to fix those.

Still need to validate the approach, but if/when the fix is added, I expect the following column configuration to give you the desired behavior for both the normal cell-entry validation and when deleting the content of cell(s) through backspace, with the 0 validation default case.

columns=[{
    'id': 'col1',
    'name': 'col1',
    'type': 'numeric',
    'on_change': {
        'action': 'coerce',
        'failure': 'default'
    },
    'validation': {
        'default': 0
    }
}]

For the table’s typing documentation.

1 Like
3

The fix & change to support this will be in the next release, dash==1.4.0.

4

Sounds great!
I am looking forward to the next release