Function case_v2

tensorflow/python/ops/control_flow_ops.py:3282–3382

Create a case operation. See also `tf.switch_case`. The `pred_fn_pairs` parameter is a list of pairs of size N. Each pair contains a boolean scalar tensor and a python callable that creates the tensors to be returned if the boolean evaluates to True. `default` is a callable generating a

(pred_fn_pairs,
            default=None,
            exclusive=False,
            strict=False,
            name="case")

@tf_export("case", v1=[])
def case_v2(pred_fn_pairs,
            default=None,
            exclusive=False,
            strict=False,
            name="case"):
  """Create a case operation.

  See also `tf.switch_case`.

  The `pred_fn_pairs` parameter is a list of pairs of size N.
  Each pair contains a boolean scalar tensor and a python callable that
  creates the tensors to be returned if the boolean evaluates to True.
  `default` is a callable generating a list of tensors. All the callables
  in `pred_fn_pairs` as well as `default` (if provided) should return the same
  number and types of tensors.

  If `exclusive==True`, all predicates are evaluated, and an exception is
  thrown if more than one of the predicates evaluates to `True`.
  If `exclusive==False`, execution stops at the first predicate which
  evaluates to True, and the tensors generated by the corresponding function
  are returned immediately. If none of the predicates evaluate to True, this
  operation returns the tensors generated by `default`.

  `tf.case` supports nested structures as implemented in
  `tf.contrib.framework.nest`. All of the callables must return the same
  (possibly nested) value structure of lists, tuples, and/or named tuples.
  Singleton lists and tuples form the only exceptions to this: when returned by
  a callable, they are implicitly unpacked to single values. This
  behavior is disabled by passing `strict=True`.

  @compatibility(v2)
  `pred_fn_pairs` could be a dictionary in v1. However, tf.Tensor and
  tf.Variable are no longer hashable in v2, so cannot be used as a key for a
  dictionary.  Please use a list or a tuple instead.
  @end_compatibility


  **Example 1:**

  Pseudocode:

  ```
  if (x < y) return 17;
  else return 23;
  ```

  Expressions:

  ```python
  f1 = lambda: tf.constant(17)
  f2 = lambda: tf.constant(23)
  r = tf.case([(tf.less(x, y), f1)], default=f2)
  ```

  **Example 2:**

  Pseudocode: