> ## Documentation Index
> Fetch the complete documentation index at: https://docs.langchain.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How to return categorical vs numerical metrics

LangSmith supports both categorical and numerical metrics, and you can return either when writing a custom evaluator.

For an evaluator result to be logged as a numerical metric, it must returned as:

* (Python only) an `int`, `float`, or `bool`
* a dict of the form `{"key": "metric_name", "score": int | float | bool}`

For an evaluator result to be logged as a categorical metric, it must be returned as:

* (Python only) a `str`
* a dict of the form `{"key": "metric_name", "value": str | int | float | bool}`

Here are some examples:

* Python: Requires `langsmith>=0.2.0`
* TypeScript: Support for multiple scores is available in `langsmith@0.1.32` and higher

<CodeGroup>
  ```python Python theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  def numerical_metric(inputs: dict, outputs: dict, reference_outputs: dict) -> float:
      # Evaluation logic...
      return 0.8
      # Equivalently
      # return {"score": 0.8}
      # Or
      # return {"key": "numerical_metric", "score": 0.8}

  def categorical_metric(inputs: dict, outputs: dict, reference_outputs: dict) -> str:
      # Evaluation logic...
      return "english"
      # Equivalently
      # return {"key": "categorical_metric", "score": "english"}
      # Or
      # return {"score": "english"}
  ```

  ```typescript TypeScript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
  import type { Run, Example } from "langsmith/schemas";

  function numericalMetric(run: Run, example: Example) {
    // Your evaluation logic here
    return { key: "numerical_metric", score: 0.8};
  }

  function categoricalMetric(run: Run, example: Example) {
    // Your evaluation logic here
    return { key: "categorical_metric", value: "english"};
  }
  ```
</CodeGroup>

## Related

* [Return multiple metrics in one evaluator](/langsmith/multiple-scores)

***

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