microsoft/qlib · error · NotImplementedError

Please implement the `exists` method

Error message

Please implement the `exists` method

What it means

exists(name) is the membership-check method of the abstract ObjManager interface (does an object with this name exist?). The base class deliberately raises NotImplementedError so every concrete backend defines its own existence semantics (file present, key present in DB, etc.).

Source

Thrown at qlib/utils/objm.py:66

            loaded object
        """
        raise NotImplementedError(f"Please implement the `load_obj` method")

    def exists(self, name: str) -> bool:
        """
        if the object named `name` exists

        Parameters
        ----------
        name : str
            name of the objecT

        Returns
        -------
        bool:
            If the object exists
        """
        raise NotImplementedError(f"Please implement the `exists` method")

    def list(self) -> list:
        """
        list the objects

        Returns
        -------
        list:
            the list of returned objects
        """
        raise NotImplementedError(f"Please implement the `list` method")

    def remove(self, fname=None):
        """remove.

        Parameters
        ----------
        fname :

View on GitHub (pinned to 79633dd950)

Solutions

1. Use FileManager, whose exists() checks the file in its managed directory.
2. Implement exists(self, name) -> bool in your subclass (e.g. return (self.path / name).exists() or a backend HEAD request).
3. If you cannot modify the class, replace the exists() call with a try/except around load_obj catching FileNotFoundError/KeyError.

Example fix

// before
if ObjManager().exists('model_v1'):  # NotImplementedError
    obj = mgr.load_obj('model_v1')

// after
if FileManager(path='./objs').exists('model_v1'):
    obj = mgr.load_obj('model_v1')

from qlib.utils.objm import ObjManager
if type(mgr).exists is ObjManager.exists:
    raise RuntimeError('manager does not implement exists(); fix subclass')

def supports_exists(mgr) -> bool:
    return type(mgr).exists is not ObjManager.exists

try:
    present = mgr.exists(name)
except NotImplementedError:
    try:
        mgr.load_obj(name)
        present = True
    except (FileNotFoundError, KeyError):
        present = False

When it happens

Trigger: ObjManager().exists('name'), or a custom subclass missing an exists override while application code calls manager.exists(name) before load_obj to avoid load errors.

Common situations: Cache-invalidation logic (`if not mgr.exists(name): save(...)`) written against a custom manager; upgrading qlib versions where exists became expected on all managers; test doubles that skip rarely-used methods.

Related errors

• Please implement `save_obj`
• Please implement the `save_objs` method
• Please implement the `load_obj` method
• Please implement the `list` method
• Please implement the `remove` method

AI-assisted analysis of microsoft/qlib@79633dd950 (2026-08-15). Data as JSON: /api/errors/cad04fee4a595d84. Report an issue: GitHub.