nautechsystems/nautilus_trader · error

Failed to get config class {config_class_name}: {e}

Error message

Failed to get config class {config_class_name}: {e}

What it means

Raised when the config module imported successfully but getattr(config_class_name) fails — the named config class is not an attribute of the module (embedded AttributeError). The node cannot build the config instance for the strategy/exec algorithm.

Source

Thrown at crates/live/src/python/node.rs:1800

        return Ok(None);
    }

    let config_parts: Vec<&str> = config_path.split(':').collect();
    if config_parts.len() != 2 {
        anyhow::bail!("config_path must be in format 'module.path:ClassName', was {config_path}");
    }
    let (config_module_name, config_class_name) = (config_parts[0], config_parts[1]);

    log::debug!(
        "Importing config class from module: {config_module_name} class: {config_class_name}"
    );

    let config_module = py
        .import(config_module_name)
        .map_err(|e| anyhow::anyhow!("Failed to import config module {config_module_name}: {e}"))?;
    let config_class = config_module
        .getattr(config_class_name)
        .map_err(|e| anyhow::anyhow!("Failed to get config class {config_class_name}: {e}"))?;

    // Convert config dict to Python dict
    let py_dict = PyDict::new(py);

    for (key, value) in config {
        let py_value = config_value_to_py(py, key, value)?;
        py_dict.set_item(key, py_value)?;
    }

    log::debug!("Created config dict: {py_dict:?}");

    // Try kwargs first, then default constructor with setattr
    let config_instance = match config_class.call((), Some(&py_dict)) {
        Ok(instance) => {
            log::debug!("Created config instance with kwargs");
            instance
        }
        Err(kwargs_err) => {

View on GitHub (pinned to 18893faf8b)

Solutions

1. Verify with python -c "from <module> import <config_class_name>"
2. Update config_path to the current module:Class name
3. Add or use the module that actually defines the config class
4. Check __init__.py re-exports if pointing at a package

Example fix

// before
config_path="myproj.cfg:StratConfig"  # renamed
// after
config_path="myproj.cfg:StrategyConfig"

import importlib
mod, cls = config_path.split(":")
assert hasattr(importlib.import_module(mod), cls), f"{cls} missing from {mod}"

def config_class_exists(config_path: str) -> bool:
    import importlib
    mod, cls = config_path.split(":")
    return hasattr(importlib.import_module(mod), cls)

try:
    node.add_strategy_from_config(cfg)
except Exception as e:
    if "Failed to get config class" in str(e):
        print("Update config_path; class not found:", cfg.config_path)
    raise

When it happens

Trigger: config_path "module:Class" where the class name is misspelled, the class was renamed/moved, or the module does not re-export it at top level.

Common situations: Renaming a *Config dataclass during refactor without updating the node config; pointing at the wrong module; expecting a re-export that isn't in __all__/__init__.

Related errors

• Invalid `external_order_claims` type: {e}
• Invalid `external_order_claims` instrument ID {claim}: {e}
• BacktestEngineConfig.controller for importable controller '{
• config_path must be in format 'module.path:ClassName', was {
• Failed to set attribute {key}: {setattr_err}

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/9ac55751da8f0cbf. Report an issue: GitHub.