nautechsystems/nautilus_trader · error · KeyError

Theme '{name}' not found.{suggestion_text} Available themes:

Error message

Theme '{name}' not found.{suggestion_text} Available themes: {available}. Register custom themes with register_theme().

What it means

get_theme raises KeyError when the requested theme name is not in the _THEMES registry. Like the chart registry, it appends difflib close-match suggestions (cutoff 0.6) and the full available list; custom themes exist only after register_theme in the same process. This is the error surfaced when TearsheetConfig.theme names an unknown theme.

Source

Thrown at python/nautilus_trader/analysis/themes.py:122

    -------
    dict[str, Any]
        Theme configuration dictionary with "template" and "colors" keys.

    Raises
    ------
    KeyError
        If the theme name is not registered.

    """
    _require_not_none(name, "name")

    if name not in _THEMES:
        available = ", ".join(_THEMES.keys())

        suggestions = get_close_matches(name, _THEMES.keys(), n=3, cutoff=0.6)
        suggestion_text = f" Did you mean: {', '.join(suggestions)}?" if suggestions else ""

        raise KeyError(
            f"Theme '{name}' not found.{suggestion_text} "
            f"Available themes: {available}. "
            f"Register custom themes with register_theme().",
        )

    theme = _THEMES[name].copy()
    theme["colors"] = theme["colors"].copy()
    return theme


def register_theme(name: str, template: str, colors: dict[str, str]) -> None:
    """
    Register a custom theme.

    Parameters
    ----------
    name : str
        The theme name for future reference.

View on GitHub (pinned to a4b06ed870)

Solutions

1. Use the suggestion hint or pick from the Available list in the message
2. List valid names: from nautilus_trader.analysis.themes import list_themes; print(list_themes())
3. For custom themes, call register_theme(name, template, colors) at startup before any get_theme/config use
4. Match casing exactly (built-ins are lowercase)

Example fix

# before
get_theme('nautilusdrak')
# KeyError: Theme 'nautilusdrak' not found. Did you mean: nautilus_dark? ...

# after
get_theme('nautilus_dark')

from nautilus_trader.analysis.themes import list_themes

if theme not in list_themes():
    raise ValueError(f'Unknown theme {theme!r}; choose from {list_themes()}')
get_theme(theme)

from nautilus_trader.analysis.themes import list_themes

def is_registered_theme(name: object) -> bool:
    return isinstance(name, str) and name in list_themes()

try:
    theme = get_theme(requested)
except KeyError as e:
    # fallback to a built-in instead of failing the whole render
    logger.warning('%s; falling back to plotly_white', e)
    theme = get_theme('plotly_white')

When it happens

Trigger: get_theme('dark') (intended 'nautilus_dark'); TearsheetConfig(theme='plotly-black') typo; referencing a theme registered in a different run/process; theme names are case-sensitive, so 'Plotly_White' also fails.

Common situations: Hand-written theme strings in configs; themes renamed between nautilus_trader versions; assuming a custom theme registered in a notebook session persists to a fresh process.

Related errors

• No tearsheet chart registered under '{chart_name}'.{hint} Re
• {name} must not be None
• Theme name cannot be empty
• Colors dict missing required keys: {missing_keys}. Required
• Chart renderer must be callable, was {type(renderer)}

AI-assisted analysis of nautechsystems/nautilus_trader@a4b06ed870 (2026-08-16). Data as JSON: /api/errors/c77f1b1d21bf7b3d. Report an issue: GitHub.