microsoft/qlib · error · NotImplementedError

Please implement the `count` method

Error message

Please implement the `count` method

What it means

BaseSingleMetric.count() is abstract. Per its docstring it must return the number of stocks excluding NaN values — unlike len(), which counts all entries. The base class only raises NotImplementedError; SingleMetric implements it. Calling .count() on a bare BaseSingleMetric raises this error.

Source

Thrown at qlib/backtest/high_performance_ds.py:269

    def __gt__(self, other: Union[BaseSingleMetric, int, float]) -> BaseSingleMetric:
        raise NotImplementedError(f"Please implement the `__gt__` method")

    def __lt__(self, other: Union[BaseSingleMetric, int, float]) -> BaseSingleMetric:
        raise NotImplementedError(f"Please implement the `__lt__` method")

    def __len__(self) -> int:
        raise NotImplementedError(f"Please implement the `__len__` method")

    def sum(self) -> float:
        raise NotImplementedError(f"Please implement the `sum` method")

    def mean(self) -> float:
        raise NotImplementedError(f"Please implement the `mean` method")

    def count(self) -> int:
        """Return the count of the single metric, NaN is not included."""

        raise NotImplementedError(f"Please implement the `count` method")

    def abs(self) -> BaseSingleMetric:
        raise NotImplementedError(f"Please implement the `abs` method")

    @property
    def empty(self) -> bool:
        """If metric is empty, return True."""

        raise NotImplementedError(f"Please implement the `empty` method")

    def add(self, other: BaseSingleMetric, fill_value: float = None) -> BaseSingleMetric:
        """Replace np.nan with fill_value in two metrics and add them."""

        raise NotImplementedError(f"Please implement the `add` method")

    def replace(self, replace_dict: dict) -> BaseSingleMetric:
        """Replace the value of metric according to replace_dict."""

View on GitHub (pinned to 79633dd950)

Solutions

1. Use SingleMetric.count() for the non-NaN stock count
2. Implement count(self) in your subclass, excluding NaN (e.g. int(self.storage.count()) if pandas-backed)
3. Distinguish from len(): use count() for statistics denominators, len() for vector size

Example fix

# before
n_valid = BaseSingleMetric(values).count()
# after
from qlib.backtest.high_performance_ds import SingleMetric
n_valid = SingleMetric(values).count()  # NaN excluded

from qlib.backtest.high_performance_ds import BaseSingleMetric
assert type(m).count is not BaseSingleMetric.count, "object does not implement count()"

def supports_count(m) -> bool:
    from qlib.backtest.high_performance_ds import BaseSingleMetric
    return isinstance(m, BaseSingleMetric) and type(m).count is not BaseSingleMetric.count

When it happens

Trigger: m.count() where m is a raw BaseSingleMetric; coverage statistics (how many stocks hold non-NaN values, e.g. number of active positions); subclasses implementing sum/mean but not count.

Common situations: Computing divisor for averages (sum/count); universe coverage diagnostics; report code that assumes pandas-like count semantics.

Related errors

• Please implement the `add` method
• Please implement the `sum` method
• Please implement the `mean` method
• Please implement the `__init__` method
• Please implement the `__add__` method

AI-assisted analysis of microsoft/qlib@79633dd950 (2026-08-15). Data as JSON: /api/errors/0e480032a7d2ccf7. Report an issue: GitHub.