microsoft/qlib · error · ValueError

No data to sync to disk.

Error message

No data to sync to disk.

What it means

Error "No data to sync to disk." thrown in microsoft/qlib.

Source

Thrown at qlib/data/cache.py:815

        This class is the proxy of the disk data.
        """

        KEY = "df"

        def __init__(self, cache_path: Union[str, Path]):
            self.index_path = cache_path.with_suffix(".index")
            self._data = None
            self.logger = get_module_logger(self.__class__.__name__)

        def get_index(self, start_time=None, end_time=None):
            # TODO: fast read index from the disk.
            if self._data is None:
                self.sync_from_disk()
            return self._data.loc[start_time:end_time].copy()

        def sync_to_disk(self):
            if self._data is None:
                raise ValueError("No data to sync to disk.")
            self._data.sort_index(inplace=True)
            self._data.to_hdf(self.index_path, key=self.KEY, mode="w", format="table")
            # The index should be readable for all users
            self.index_path.chmod(stat.S_IRWXU | stat.S_IRGRP | stat.S_IROTH)

        def sync_from_disk(self):
            # The file will not be closed directly if we read_hdf from the disk directly
            with pd.HDFStore(self.index_path, mode="r") as store:
                if "/{}".format(self.KEY) in store.keys():
                    self._data = pd.read_hdf(store, key=self.KEY)
                else:
                    self._data = pd.DataFrame()

        def update(self, data, sync=True):
            self._data = data.astype(np.int32).copy()
            if sync:
                self.sync_to_disk()

View on GitHub (pinned to 79633dd950)

Solutions

1. Ensure there is data in the cache before calling sync/flush to disk.
2. Check that the cache was populated (e.g. features were queried) before triggering the sync.

When it happens

Trigger: This error is raised at qlib/data/cache.py:815 when the guard condition fails: "No data to sync to disk.". It triggers when the code path receives input or a state that violates the precondition checked at this point — e.g. an unimplemented abstract method being called, an unsupported argument type/value, or an invalid configuration. To avoid it, satisfy the documented precondition before this call: implement the required method in your subclass, or pass a supported value of the expected type as described by the message.

Common situations: See trigger scenarios.

AI-assisted analysis of microsoft/qlib@79633dd950 (2026-08-15). Data as JSON: /api/errors/97d15b7275cb5e5a. Report an issue: GitHub.