keras-team/keras · error · ValueError

`sparse=True` can only be used with the TensorFlow backend.

Error message

`sparse=True` can only be used with the TensorFlow backend.

What it means

Error "`sparse=True` can only be used with the TensorFlow backend." thrown in keras-team/keras.

Source

Thrown at keras/src/layers/preprocessing/string_lookup.py:325

        oov_token="[UNK]",
        vocabulary=None,
        idf_weights=None,
        invert=False,
        output_mode="int",
        pad_to_max_tokens=False,
        sparse=False,
        encoding="utf-8",
        name=None,
        salt=None,
        **kwargs,
    ):
        if not tf.available:
            raise ImportError(
                "Layer StringLookup requires TensorFlow. "
                "Install it via `pip install tensorflow`."
            )
        if sparse and backend.backend() != "tensorflow":
            raise ValueError(
                "`sparse=True` can only be used with the TensorFlow backend."
            )
        self.encoding = encoding
        super().__init__(
            max_tokens=max_tokens,
            num_oov_indices=num_oov_indices,
            mask_token=mask_token,
            oov_token=oov_token,
            vocabulary=vocabulary,
            idf_weights=idf_weights,
            invert=invert,
            output_mode=output_mode,
            pad_to_max_tokens=pad_to_max_tokens,
            sparse=sparse,
            name=name,
            salt=salt,
            vocabulary_dtype="string",
            **kwargs,

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/layers/preprocessing/string_lookup.py:325 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of keras-team/keras@7a34a03db6 (2026-08-25). Data as JSON: /api/errors/817e1aa3681d6ae0. Report an issue: GitHub.