Updating ui.table columns only works once

[falkoschindler]

Description

As noticed by rafik1200 on Reddit, the following code allows to switch table columns only once:

columns_a = [{'name': 'id', 'label': 'ID A', 'field': 'id'}]
columns_b = [{'name': 'id', 'label': 'ID B', 'field': 'id'}]

def toggle_headers(button_name: str):
    table.columns = columns_a if button_name == 'A' else columns_b

table = ui.table(columns=columns_a, rows=[])
ui.button('A', on_click=lambda: toggle_headers('A'))
ui.button('B', on_click=lambda: toggle_headers('B'))

In contrast, it works when re-creating the list of columns every time:

def toggle_headers(button_name: str):
    table.columns = [{'name': 'id', 'label': f'ID {button_name}', 'field': 'id'}]

table = ui.table(columns=[{'name': 'id', 'label': 'ID A', 'field': 'id'}], rows=[])
ui.button('A', on_click=lambda: toggle_headers('A'))
ui.button('B', on_click=lambda: toggle_headers('B'))

[falkoschindler]

https://www.reddit.com/r/nicegui/comments/1gcqt3m/comment/lu5zip5/

Oh, I think I understand! When passing a list of columns to ui.table, the table uses a reference to the original list. This allows doing things like

columns = [{'name': 'id', 'label': 'ID', 'field': 'id'}]

def change_label():
    columns[0]['label'] = 'X'
    table.update()

table = ui.table(columns=columns, rows=[])
ui.button('Change label', on_click=change_label)

But it also means that by assigning columns_b, the original list columns_a is overwritten. In this a bit unexpected, but when developing the new API for ui.table in version 2.0.0, we somehow couldn't come up with a solution that behaves nicely in all circumstances.

A workaround is to make sure to assign copies instead of the original lists:

columns_a = [{'name': 'id', 'label': 'ID A', 'field': 'id'}]
columns_b = [{'name': 'id', 'label': 'ID B', 'field': 'id'}]

def toggle_headers(button_name: str):
    table.columns = columns_a[:] if button_name == 'A' else columns_b[:]

table = ui.table(columns=columns_a[:], rows=[])
ui.button('A', on_click=lambda: toggle_headers('A'))
ui.button('B', on_click=lambda: toggle_headers('B'))

Can we do anything about it? Or should we simply close the issue?

[falkoschindler]

Let's close this issue since it's expected behavior.