streamlit/streamlit · error · StreamlitInvalidThemeOptionError

Theme option '{option_name}[{i}]' must be a string, got {typ

Error message

Theme option '{option_name}[{i}]' must be a string, got {type(color).__name__}: {color}

What it means

Error "Theme option '{option_name}[{i}]' must be a string, got {type(color).__name__}: {color}" thrown in streamlit/streamlit.

Source

Thrown at lib/streamlit/config_util.py:277

        empty values in the case of arrays.

    Notes
    -----
    Logs warnings for potentially invalid colors, since more comprehensive
    validation happens on the frontend.
    """
    logger = _get_logger()

    # Handle array color options (chartCategoricalColors, chartSequentialColors)
    if isinstance(value, list):
        if not value:
            raise StreamlitInvalidThemeOptionError(
                f"Theme option '{option_name}' cannot be an empty array"
            )

        for i, color in enumerate(value):
            if not isinstance(color, str):
                raise StreamlitInvalidThemeOptionError(
                    f"Theme option '{option_name}[{i}]' must be a string, got {type(color).__name__}: {color}"
                )

            color_str = color.strip()
            if not color_str:
                raise StreamlitInvalidThemeOptionError(
                    f"Theme option '{option_name}[{i}]' cannot be empty"
                )

            # Lightweight color validation with warning
            if not is_css_color_like(color_str):
                logger.warning(
                    "Theme option '%s[%s]' may be an invalid color: %s. "
                    "Expected formats: hex, rgb, and rgba colors",
                    option_name,
                    i,
                    color_str,
                )

View on GitHub (pinned to 202661fc55)

When it happens

Trigger: Thrown at lib/streamlit/config_util.py:277 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of streamlit/streamlit@202661fc55 (2026-08-26). Data as JSON: /api/errors/4e14916d4cd4c9ac. Report an issue: GitHub.