keras-team/keras · error · ValueError

not a valid gufunc signature: {signature}

Error message

not a valid gufunc signature: {signature}

What it means

Error "not a valid gufunc signature: {signature}" thrown in keras-team/keras.

Source

Thrown at keras/src/backend/common/backend_utils.py:475

        )
    return shifts, axes


### Code for ops.vectorize() used for TF and torch backends.

# See http://docs.scipy.org/doc/numpy/reference/c-api.generalized-ufuncs.html
_DIMENSION_NAME = r"\w+"
_CORE_DIMENSION_LIST = "(?:{0:}(?:,{0:})*)?".format(_DIMENSION_NAME)
_ARGUMENT = rf"\({_CORE_DIMENSION_LIST}\)"
_ARGUMENT_LIST = "{0:}(?:,{0:})*".format(_ARGUMENT)
_SIGNATURE = "^{0:}->{0:}$".format(_ARGUMENT_LIST)


def _vectorize_parse_gufunc_signature(
    signature,
):
    if not re.match(_SIGNATURE, signature):
        raise ValueError(f"not a valid gufunc signature: {signature}")
    args, retvals = (
        [
            tuple(re.findall(_DIMENSION_NAME, arg))
            for arg in re.findall(_ARGUMENT, arg_list)
        ]
        for arg_list in signature.split("->")
    )
    return args, retvals


def _vectorize_update_dim_sizes(dim_sizes, shape, core_dims, is_input=True):
    num_core_dims = len(core_dims)
    if is_input:
        if len(shape) < num_core_dims:
            raise ValueError(
                f"input with shape {shape} does not "
                "have enough dimensions for all core "
                f"dimensions {core_dims}"

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/backend/common/backend_utils.py:475 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/4a56051e8049656d. Report an issue: GitHub.