# tf.summary.scalar

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| [![](https://www.tensorflow.org/images/tf_logo_32px.png) TensorFlow 1 version](https://www.tensorflow.org/versions/r1.15/api_docs/python/tf/summary/scalar) | [![](https://www.tensorflow.org/images/GitHub-Mark-32px.png) View source on GitHub](https://github.com/tensorflow/tensorboard/tree/master/tensorboard/plugins/scalar/summary_v2.py) |

Write a scalar summary.

    tf.summary.scalar(
        name, data, step=None, description=None
    )

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| ## Arguments ||
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| `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/versions/r2.0/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. |

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

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| ## Raises ||
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| `ValueError` | if a default writer exists, but no step was provided and [`tf.summary.experimental.get_step()`](https://www.tensorflow.org/versions/r2.0/api_docs/python/tf/summary/experimental/get_step) is None. |

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