# python: derive
URL: https://generaltranslation.com/en-GB/docs/python/api/derive.mdx
---
title: derive
description: API reference for the derive function
---

## Overview

`derive` marks content as statically analysable so that the GT CLI can extract all possible translation entries at build time.

It is an **identity function** — it returns exactly what you pass in. Its purpose is to serve as a marker for static analysis.

```python
from gt_flask import derive, t  # or from gt_fastapi

message = t(f"The {derive('boy' if gender == 'male' else 'girl')} is playing.")
```


## Reference

### Parameters

<TypeTable
  type={{
  "content": {
    type: 'object',
    description: 'A static expression with a finite set of possible values.',
  },
}}
/>

### Returns

Returns `content` unchanged. The function is an identity — its purpose is to serve as a marker for the CLI.

***

## Notes

* All possible outcomes must be statically analysable at build time
* Dynamic content (user input, API data) inside `derive` should be wrapped with [`declare_var`](/docs/python/api/declare-var)
* Use [`decode_vars`](/docs/python/api/decode-vars) to extract original values from declared variables
* See the [derive tutorial](/docs/python/tutorials/derive) for detailed examples and usage patterns