keras-team/keras · error · ValueError

Invalid data_format: {self.data_format}. Expected 'channels_

Error message

Invalid data_format: {self.data_format}. Expected 'channels_first' or 'channels_last'.

What it means

Error "Invalid data_format: {self.data_format}. Expected 'channels_first' or 'channels_last'." thrown in keras-team/keras.

Source

Thrown at keras/src/layers/pooling/base_adaptive_pooling.py:24

class BaseAdaptivePooling(Layer):
    """Base class shared by all adaptive pooling layers."""

    def __init__(self, output_size, data_format=None, **kwargs):
        """Initialize base adaptive pooling layer.

        Args:
            output_size: Normalized spatial output size as a tuple
                (for example, (32,), (32, 32), or (32, 32, 32)).
            data_format: Either "channels_last" or "channels_first".
            **kwargs: Additional layer keyword arguments.
        """
        super().__init__(**kwargs)
        self.output_size = output_size
        self.data_format = data_format or config.image_data_format()
        if self.data_format not in {"channels_first", "channels_last"}:
            raise ValueError(
                f"Invalid data_format: {self.data_format}. "
                "Expected 'channels_first' or 'channels_last'."
            )

    def compute_output_shape(self, input_shape):
        """Return the output shape tensor after pooling."""
        batch_size = input_shape[0]
        if self.data_format == "channels_last":
            channels = input_shape[-1]
            return (batch_size, *self.output_size, channels)
        else:
            channels = input_shape[1]
            return (batch_size, channels, *self.output_size)

    def get_config(self):
        config_dict = {
            "output_size": self.output_size,
            "data_format": self.data_format,

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/layers/pooling/base_adaptive_pooling.py:24 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/6f7e13547a885a48. Report an issue: GitHub.