OpenBB-finance/OpenBB · error · ValueError

Label must be specified

Error message

Label must be specified

What it means

In OpenBBFigure.add_legend_label (openbb_figure.py:801), after the trace-lookup block the method requires a truthy `label` — the visible text of the dummy scatter it adds to build the legend entry. An empty/None label makes the legend entry invisible and meaningless, so it raises ValueError("Label must be specified").

Source

Thrown at openbb_platform/obbject_extensions/charting/openbb_charting/core/openbb_figure.py:801

            If label is not specified and trace is not specified
        """
        if trace:
            for trace_ in self.data:
                if trace_.name == trace:  # type: ignore
                    for arg, default in zip(
                        [label, mode, marker, line_dash],
                        [trace, trace_.mode, trace_.marker, trace_.line_dash],  # type: ignore
                    ):
                        if not arg and default:
                            arg = default  # noqa: PLW2901

                    kwargs.update(dict(yaxis=trace_.yaxis))  # type: ignore
                    break
            else:
                raise ValueError(f"Trace '{trace}' not found")

        if not label:
            raise ValueError("Label must be specified")

        self.add_scatter(
            x=[None],
            y=[None],
            mode=mode or "lines",
            name=label,
            marker=marker or dict(),
            line_dash=line_dash or "solid",
            legendrank=legendrank,
            **kwargs,
        )

    def show(  # noqa: PLR0915
        self,
        *args,
        external: bool = False,
        export_image: Path | str | None = "",  # pylint: disable=W0613
        **kwargs,

View on GitHub (pinned to 3e071fcc2c)

Solutions

  1. Pass a non-empty label: fig.add_legend_label(label="200D MA").
  2. Default it from config: label = cfg.get("label") or "unnamed series".
  3. Skip the call entirely when no label is available — a legend entry without text serves no purpose.

Example fix

# before
fig.add_legend_label(trace="sma", label=cfg.get("text"))  # None -> ValueError

# after
label = cfg.get("text") or cfg.get("label")
if label:
    fig.add_legend_label(trace="sma", label=label)
Defensive patterns

Strategy: validation

Validate before calling

label = label or cfg.get("text") or ""
if label:
    fig.add_legend_label(trace=trace, label=label)

Type guard

def valid_legend_label(label) -> bool:
    return isinstance(label, str) and bool(label.strip())

Try / catch

try:
    fig.add_legend_label(trace=trace, label=label)
except ValueError as e:
    if "Label must be specified" in str(e):
        pass  # nothing to show
    else:
        raise

Prevention

When it happens

Trigger: Calling add_legend_label() with no arguments, or with label=""/None — including code that reads the label from a config key that is absent and defaults to None.

Common situations: Programmatic loops over indicator configs where some entries lack a label field; refactors that renamed the parameter (e.g. text->label) leaving the old call shape.

Related errors

AI-assisted analysis of OpenBB-finance/OpenBB@3e071fcc2c (2026-08-14). Data as JSON: /api/errors/ab98b5d78db3a0a8. Report an issue: GitHub.