|---| | [ View source on GitHub](https://github.com/tensorflow/tensorflow/blob/v2.21.0/tensorflow/python/summary/tb_summary.py#L243-L299) | Write a scalar summary. tf.summary.scalar( name, data, step=None, description=None ) ### Used in the notebooks | Used in the tutorials | |---| | - [pix2pix: Image-to-image translation with a conditional GAN](https://www.tensorflow.org/tutorials/generative/pix2pix) - [TensorBoard Scalars: Logging training metrics in Keras](https://www.tensorflow.org/tensorboard/scalars_and_keras) - [Get started with TensorBoard](https://www.tensorflow.org/tensorboard/get_started) - [Research tools](https://www.tensorflow.org/quantum/tutorials/research_tools) - [Migrating tf.summary usage to TF 2.x](https://www.tensorflow.org/tensorboard/migrate) | See also [`tf.summary.image`](https://www.tensorflow.org/api_docs/python/tf/summary/image), [`tf.summary.histogram`](https://www.tensorflow.org/api_docs/python/tf/summary/histogram), [`tf.summary.SummaryWriter`](https://www.tensorflow.org/api_docs/python/tf/summary/SummaryWriter). Writes simple numeric values for later analysis in TensorBoard. Writes go to the current default summary writer. Each summary point is associated with an integral `step` value. This enables the incremental logging of time series data. A common usage of this API is to log loss during training to produce a loss curve. #### For example: test_summary_writer = tf.summary.create_file_writer('test/logdir') with test_summary_writer.as_default(): tf.summary.scalar('loss', 0.345, step=1) tf.summary.scalar('loss', 0.234, step=2) tf.summary.scalar('loss', 0.123, step=3) Multiple independent time series may be logged by giving each series a unique `name` value. See [Get started with TensorBoard](https://www.tensorflow.org/tensorboard/get_started) for more examples of effective usage of [`tf.summary.scalar`](https://www.tensorflow.org/api_docs/python/tf/summary/scalar). In general, this API expects that data points are logged with a monotonically increasing step value. Duplicate points for a single step or points logged out of order by step are not guaranteed to display as desired in TensorBoard.


| ## Arguments || |---|---| | `name` | A name for this summary. The summary tag used for TensorBoard will be this name prefixed by any active name scopes. | | `data` | A real numeric scalar value, convertible to a `float32` Tensor. | | `step` | Explicit `int64`-castable monotonic step value for this summary. If omitted, this defaults to [`tf.summary.experimental.get_step()`](https://www.tensorflow.org/api_docs/python/tf/summary/experimental/get_step), which must not be None. | | `description` | Optional long-form description for this summary, as a constant `str`. Markdown is supported. Defaults to empty. |



| ## Returns || |---|---| | True on success, or false if no summary was written because no default summary writer was available. ||



| ## Raises || |---|---| | `ValueError` | if a default writer exists, but no step was provided and [`tf.summary.experimental.get_step()`](https://www.tensorflow.org/api_docs/python/tf/summary/experimental/get_step) is None. |