How to remove a column from a DataTable?

[simon-b]

The docstring for DataTable.add_column implies that columns can also be removed:

Uniquely identifies this column. Can be used to retrieve this column regardless of its current location in the DataTable (it could have moved after being added due to sorting/insertion/deletion of other columns).

textual/src/textual/widgets/_data_table.py

Line 1274 in c2f0771

after being added due to sorting/insertion/deletion of other columns).

But, it's not clear how to actually remove columns, if it's even possible.

A very naive approach is just to del from DataTable.columns:

from textual.app import App, ComposeResult
from textual.widgets import DataTable

ROWS = [
    ("lane", "swimmer", "country", "time"),
    (4, "Joseph Schooling", "Singapore", 50.39),
    (2, "Michael Phelps", "United States", 51.14),
    (5, "Chad le Clos", "South Africa", 51.14),
    (6, "László Cseh", "Hungary", 51.14),
    (3, "Li Zhuhao", "China", 51.26),
    (8, "Mehdy Metella", "France", 51.58),
    (7, "Tom Shields", "United States", 51.73),
    (1, "Aleksandr Sadovnikov", "Russia", 51.84),
    (10, "Darren Burns", "Scotland", 51.84),
]


class TableApp(App):
    def compose(self) -> ComposeResult:
        yield DataTable()

    def on_mount(self) -> None:
        table = self.query_one(DataTable)
        table.add_columns(*ROWS[0])
        table.add_rows(ROWS[1:])

    def on_data_table_header_selected(self, event:DataTable.HeaderSelected):
        table = self.query_one(DataTable)
        del table.columns[event.column_key]  # <- `del` the clicked column


app = TableApp()
if __name__ == "__main__":
    app.run()

This sort-of works for the right-most column, but sometimes results in visual artefacts.

For central columns then we get an exception, I assume because _column_locations is not updated and still refers to the non-existent central column at a relevant index.

╭────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────────────────────────────╮
│                                           python3.9/site-packages/textual/widgets/_data_table.py:1982 in _on_mouse_move                │
│                                                                                                                                        │
│   1979 │   def _on_mouse_move(self, event: events.MouseMove):                                                                          │
│   1980 │   │   """If the hover cursor is visible, display it by extracting the row                                                     │
│   1981 │   │   and column metadata from the segments present in the cells."""                                                          │
│ ❱ 1982 │   │   self._set_hover_cursor(True)                                                                                            │
│   1983 │   │   meta = event.style.meta                                                                                                 │
│   1984 │   │                                                                                                                           │
│   1985 │   │   if meta and self.show_cursor and self.cursor_type != "none":                                                            │
│                                                                                                                                        │
│ ╭──────────────── locals ─────────────────╮                                                                                            │
│ │ event = MouseMove(x=35, y=1, delta_x=1) │                                                                                            │
│ │  self = DataTable()                     │                                                                                            │
│ ╰─────────────────────────────────────────╯                                                                                            │
│                                                                                                                                        │
│                                           python3.9/site-packages/textual/widgets/_data_table.py:2074 in _set_hover_cursor             │
│                                                                                                                                        │
│   2071 │   │   elif cursor_type == "row":                                                       ╭───────── locals ──────────╮          │
│   2072 │   │   │   self.refresh_row(self.hover_row)                                             │      active = True        │          │
│   2073 │   │   elif cursor_type == "cell":                                                      │ cursor_type = 'cell'      │          │
│ ❱ 2074 │   │   │   self.refresh_coordinate(self.hover_coordinate)                               │        self = DataTable() │          │
│   2075 │                                                                                        ╰───────────────────────────╯          │
│   2076 │   async def _on_click(self, event: events.Click) -> None:                                                                     │
│   2077 │   │   self._set_hover_cursor(True)                                                                                            │
│                                                                                                                                        │
│                                           python3.9/site-packages/textual/widgets/_data_table.py:1468 in refresh_coordinate            │
│                                                                                                                                        │
│   1465 │   │   """                                                                                                                     │
│   1466 │   │   if not self.is_valid_coordinate(coordinate):                                                                            │
│   1467 │   │   │   return self                                                                                                         │
│ ❱ 1468 │   │   region = self._get_cell_region(coordinate)                                                                              │
│   1469 │   │   self._refresh_region(region)                                                                                            │
│   1470 │   │   return self                                                                                                             │
│   1471                                                                                                                                 │
│                                                                                                                                        │
│ ╭───────────────── locals ─────────────────╮                                                                                           │
│ │ coordinate = Coordinate(row=0, column=2) │                                                                                           │
│ │       self = DataTable()                 │                                                                                           │
│ ╰──────────────────────────────────────────╯                                                                                           │
│                                                                                                                                        │
│                                           python3.9/site-packages/textual/widgets/_data_table.py:1178 in _get_cell_region              │
│                                                                                                                                        │
│   1175 │   │   # The x-coordinate of a cell is the sum of widths of the data cells to the left                                         │
│   1176 │   │   # plus the width of the render width of the longest row label.                                                          │
│   1177 │   │   x = (                                                                                                                   │
│ ❱ 1178 │   │   │   sum(column.render_width for column in self.ordered_columns[:column_index])                                          │
│   1179 │   │   │   + self._row_label_column_width                                                                                      │
│   1180 │   │   )                                                                                                                       │
│   1181 │   │   column_key = self._column_locations.get_key(column_index)                                                               │
│                                                                                                                                        │
│ ╭───────────────────────────── locals ─────────────────────────────╮                                                                   │
│ │ column_index = 2                                                 │                                                                   │
│ │   coordinate = Coordinate(row=0, column=2)                       │                                                                   │
│ │          row = Row(key=RowKey(value=None), height=1, label=None) │                                                                   │
│ │    row_index = 0                                                 │                                                                   │
│ │      row_key = RowKey(value=None)                                │                                                                   │
│ │         self = DataTable()                                       │                                                                   │
│ ╰──────────────────────────────────────────────────────────────────╯                                                                   │
│                                                                                                                                        │
│                                           python3.9/site-packages/textual/widgets/_data_table.py:1561 in ordered_columns               │
│                                                                                                                                        │
│   1558 │   │   column_keys = [                                                                                                         │
│   1559 │   │   │   self._column_locations.get_key(index) for index in column_indices                                                   │
│   1560 │   │   ]                                                                                                                       │
│ ❱ 1561 │   │   ordered_columns = [self.columns[key] for key in column_keys]                                                            │
│   1562 │   │   return ordered_columns                                                                                                  │
│   1563 │                                                                                                                               │
│   1564 │   @property                                                                                                                   │
│                                                                                                                                        │
│ ╭──────────────────────────────────────── locals ────────────────────────────────────────╮                                             │
│ │ column_indices = range(0, 3)                                                           │                                             │
│ │    column_keys = [ColumnKey(value=None), ColumnKey(value=None), ColumnKey(value=None)] │                                             │
│ │           self = DataTable()                                                           │                                             │
│ ╰────────────────────────────────────────────────────────────────────────────────────────╯                                             │
│                                                                                                                                        │
│                                           python3.9/site-packages/textual/widgets/_data_table.py:1561 in <listcomp>                    │
│                                                                                                                                        │
│   1558 │   │   column_keys = [                                                                                                         │
│   1559 │   │   │   self._column_locations.get_key(index) for index in column_indices                                                   │
│   1560 │   │   ]                                                                                                                       │
│ ❱ 1561 │   │   ordered_columns = [self.columns[key] for key in column_keys]                                                            │
│   1562 │   │   return ordered_columns                                                                                                  │
│   1563 │                                                                                                                               │
│   1564 │   @property                                                                                                                   │
│                                                                                                                                        │
│ ╭─────────────────── locals ───────────────────╮                                                                                       │
│ │   .0 = <list_iterator object at 0x10493ae50> │                                                                                       │
│ │  key = ColumnKey(value=None)                 │                                                                                       │
│ │ self = DataTable()                           │                                                                                       │
│ ╰──────────────────────────────────────────────╯                                                                                       │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
KeyError: <textual.widgets._data_table.ColumnKey object at 0x10487d8b0>

Is there a more robust way to remove columns?

[TomJGooding]

A DataTable.remove_column method has been added in the latest version announced today!