microsoft/qlib · error · NotImplementedError

Please implement the `_get_exp` method

Error message

Please implement the `_get_exp` method

What it means

_get_exp is the protected retrieval hook of ExpManager: concrete managers resolve experiment_id/experiment_name to an Experiment or raise ValueError. The base body raises NotImplementedError, so this error indicates the lookup ran on an abstract or incompletely implemented manager rather than MLflowExpManager.

Solutions

1. Ensure qlib.init uses MLflowExpManager (default) so _get_exp resolves via client.get_experiment.
2. Implement _get_exp(self, experiment_id=None, experiment_name=None) in your subclass returning your Experiment type or raising ValueError.
3. Use the public R.get_exp / exp_manager.get_exp API and implement every private hook they depend on.

Example fix

# before
class MyManager(ExpManager):
    pass
exp = MyManager().get_exp(experiment_name='e')  # base _get_exp -> NotImplementedError

# after
class MyManager(ExpManager):
    def _get_exp(self, experiment_id=None, experiment_name=None):
        exp = self.client.get_experiment_by_name(experiment_name) if experiment_name else self.client.get_experiment(experiment_id)
        if exp is None:
            raise ValueError('No valid experiment has been found')
        return MyExperiment(exp.experiment_id, exp.name, self.uri)

from qlib.workflow.expm import ExpManager
assert R.exp_manager.__class__._get_exp is not ExpManager._get_exp, 'experiment lookup not implemented'

def manager_can_get_exp(mgr) -> bool:
    from qlib.workflow.expm import ExpManager
    return mgr.__class__._get_exp is not ExpManager._get_exp

When it happens

Trigger: R.get_exp(...) delegating to a manager subclass that overrides get_exp but not _get_exp; directly invoking exp_manager._get_exp(...) in custom code or tests.

Common situations: Writing a custom manager backend and missing the private hook despite implementing the public API; scaffolding generated by copying only part of MLflowExpManager.

Related errors

• Please implement the `create_exp` method.
• Please implement the `delete_exp` method.
• Please implement the `end_exp` method.
• Please implement the `_get_recorder` method
• Please implement the `list_experiments` method.

AI-assisted analysis of microsoft/qlib@79633dd950 (2026-08-15). Data as JSON: /api/errors/86aa9c82d8e690c1. Report an issue: GitHub.

Appendix: source

Thrown at qlib/workflow/expm.py:267

        Get specific experiment by name or id. If it does not exist, raise ValueError.

        Parameters
        ----------
        experiment_id :
            The id of experiment
        experiment_name :
            The name of experiment

        Returns
        -------
        Experiment:
            The searched experiment

        Raises
        ------
        ValueError
        """
        raise NotImplementedError(f"Please implement the `_get_exp` method")

    def delete_exp(self, experiment_id=None, experiment_name=None):
        """
        Delete an experiment.

        Parameters
        ----------
        experiment_id  : str
            the experiment id.
        experiment_name  : str
            the experiment name.
        """
        raise NotImplementedError(f"Please implement the `delete_exp` method.")

    @property
    def default_uri(self):
        """
        Get the default tracking URI from qlib.config.C

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