microsoft/qlib · error · NotImplementedError

Please implement the `first_tasks` method.

Error message

Please implement the `first_tasks` method.

What it means

OnlineStrategy.first_tasks is an abstract hook that the base class deliberately leaves unimplemented. It is called once at the start of an online workflow (e.g. OnlineManager.first_tasks / routine initialization) to seed the initial batch of tasks, so any subclass that does not override first_tasks will crash with this NotImplementedError.

Source

Thrown at qlib/workflow/online/strategy.py:76

            2. Switch models at the `test_start` (at time timestamp `T + 1` typically)

        Args:
            models (list): a list of models.
            cur_time (pd.Dataframe): current time from OnlineManger. None for the latest.

        Returns:
            List[object]: a list of online models.
        """
        if not trained_models:
            return self.tool.online_models()
        self.tool.reset_online_tag(trained_models)
        return trained_models

    def first_tasks(self) -> List[dict]:
        """
        Generate a series of tasks firstly and return them.
        """
        raise NotImplementedError(f"Please implement the `first_tasks` method.")

    def get_collector(self) -> Collector:
        """
        Get the instance of `Collector <../advanced/task_management.html#Task Collecting>`_ to collect different results of this strategy.

        For example:
            1) collect predictions in Recorder
            2) collect signals in a txt file

        Returns:
            Collector
        """
        raise NotImplementedError(f"Please implement the `get_collector` method.")


class RollingStrategy(OnlineStrategy):
    """
    This example strategy always uses the latest rolling model sas online models.

View on GitHub (pinned to 79633dd950)

Solutions

1. Implement first_tasks() -> List[dict] in your subclass returning the initial task configurations to train
2. Use RollingStrategy (it implements first_tasks by filling the task template with the rolling generator) if rolling retraining fits your case
3. Check the method name and that it takes no extra required arguments

Example fix

# before
class MyStrategy(OnlineStrategy):
    def prepare_tasks(self, cur_time, **kwargs):
        return []
    # first_tasks missing

# after
class MyStrategy(OnlineStrategy):
    def prepare_tasks(self, cur_time, **kwargs):
        return []
    def first_tasks(self) -> List[dict]:
        return [self.task_template]

from qlib.workflow.online.strategy import OnlineStrategy

def assert_first_tasks_implemented(strategy):
    if strategy.first_tasks.__func__ is OnlineStrategy.first_tasks:
        raise TypeError(f'{type(strategy).__name__} must implement first_tasks')

from qlib.workflow.online.strategy import OnlineStrategy

def has_first_tasks(strategy) -> bool:
    return strategy.first_tasks.__func__ is not OnlineStrategy.first_tasks

try:
    tasks = strategy.first_tasks()
except NotImplementedError:
    tasks = []  # or re-raise: strategy is incomplete by contract

When it happens

Trigger: Instantiating a custom OnlineStrategy subclass that overrides some hooks but not first_tasks, then triggering the initial task generation; calling strategy.first_tasks() directly; misspelling the override (e.g. first_task).

Common situations: Building a custom online strategy and forgetting the bootstrap hook; adapting RollingStrategy code and deleting its first_tasks implementation; assuming the base class has a default implementation.

Related errors

• Please implement the `prepare_tasks` method.
• Please implement the `get_all_stock` method
• Please implement the `get_data` method
• Please implement the `__init__` method
• Subclass of SeriesDFilter must reimplement `getFilterSeries`

AI-assisted analysis of microsoft/qlib@79633dd950 (2026-08-15). Data as JSON: /api/errors/07fec29aa3cb6091. Report an issue: GitHub.