Textualize/textual · error · ValueError

'pane_id' must be a non-empty string or a TabPane with an id

Error message

'pane_id' must be a non-empty string or a TabPane with an id.

What it means

Raised by TabbedContent.get_tab when pane_id is neither a non-empty string nor an object (TabPane) with a truthy .id. The method needs an id to look up the tab in the ContentTabs child, so an empty string or an id-less TabPane fails.

Source

Thrown at src/textual/widgets/_tabbed_content.py:593

    def tab_count(self) -> int:
        """Total number of tabs."""
        return self.get_child_by_type(ContentTabs).tab_count

    def get_tab(self, pane_id: str | TabPane) -> Tab:
        """Get the `Tab` associated with the given ID or `TabPane`.

        Args:
            pane_id: The ID of the pane, or the pane itself.

        Returns:
            The Tab associated with the ID.

        Raises:
            ValueError: Raised if no ID was available.
        """
        if target_id := (pane_id if isinstance(pane_id, str) else pane_id.id):
            return self.get_child_by_type(ContentTabs).get_content_tab(target_id)
        raise ValueError(
            "'pane_id' must be a non-empty string or a TabPane with an id."
        )

    def get_pane(self, pane_id: str | ContentTab) -> TabPane:
        """Get the `TabPane` associated with the given ID or tab.

        Args:
            pane_id: The ID of the pane to get, or the Tab it is associated with.

        Returns:
            The `TabPane` associated with the ID or the given tab.

        Raises:
            ValueError: Raised if no ID was available.
        """
        target_id: str | None = None
        if isinstance(pane_id, ContentTab):
            target_id = (

View on GitHub (pinned to 06dbeef4bb)

Solutions

1. Give every TabPane an explicit id: TabPane('Title', id='pane-one').
2. Guard: check pane.id is truthy before calling get_tab.
3. Pass the known string id instead of the pane object.

Example fix

# before
TabPane('Settings')  # no id
# ...
tabbed_content.get_tab(tabbed_content.active_pane)  # raises
# after
TabPane('Settings', id='settings')
# ...
tabbed_content.get_tab('settings')

pane_id = pane_id if isinstance(pane_id, str) else pane_id.id
if pane_id:
    tab = tabbed_content.get_tab(pane_id)

try:
    tab = tabbed_content.get_tab(pane_id)
except ValueError:
    tab = None

When it happens

Trigger: get_tab(tabbed_content.active_pane) where the TabPane has no id set; get_tab('') ; passing a TabPane constructed without id=.

Common situations: Querying the tab for the active pane when panes were created without ids, or programmatic tab lookup with user-supplied ids that may be empty.

Related errors

• 'pane_id' must be a non-empty string or a ContentTab with an
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AI-assisted analysis of Textualize/textual@06dbeef4bb (2026-08-27). Data as JSON: /api/errors/af17d8d63f3e77e6. Report an issue: GitHub.