Defined in tensorflow/python/framework/

See the guide: Utilities (contrib) > Miscellaneous Utility Functions

Returns the constant value of the given tensor, if efficiently calculable.

This function attempts to partially evaluate the given tensor, and returns its value as a numpy ndarray if this succeeds.

TODO(mrry): Consider whether this function should use a registration mechanism like gradients and ShapeFunctions, so that it is easily extensible.

NOTE: If constant_value(tensor) returns a non-None result, it will no longer be possible to feed a different value for tensor. This allows the result of this function to influence the graph that is constructed, and permits static shape optimizations.


  • tensor: The Tensor to be evaluated.
  • partial: If True, the returned numpy array is allowed to have partially evaluated values. Values that can't be evaluated will be None.


A numpy ndarray containing the constant value of the given tensor, or None if it cannot be calculated.


  • TypeError: if tensor is not an ops.Tensor.