Defined in tensorflow/contrib/data/python/ops/

A transformation that groups elements and performs a reduction.

This transformation maps element of a dataset to a key using key_func and groups the elements by key. The reducer is used to process each group; its init_func is used to initialize state for each group when it is created, the reduce_func is used to update the state every time an element is mapped to the matching group, and the finalize_func is used to map the final state to an output value.


  • key_func: A function mapping a nested structure of tensors (having shapes and types defined by self.output_shapes and self.output_types) to a scalar tf.int64 tensor.
  • reducer: An instance of Reducer, which captures the reduction logic using the init_func, reduce_func, and finalize_func functions.


A Dataset transformation function, which can be passed to