# General Translation Python SDKs: declare_var
URL: https://generaltranslation.com/en-GB/docs/python/reference/functions/declare-var.mdx
---

title: declare_var
description: Mark a dynamic value as a non-translatable variable in General Translation Python. API reference for declare_var.

---

Marks a dynamic value as a non-translatable variable so it is preserved across languages. Use it for values known only at runtime, such as user names, email addresses, and counts, embedded inside a [`t`](/docs/python/reference/functions/t) call.

## Overview [#overview]

Call `declare_var` with a value and an optional keyword-only `name`. It returns an ICU `{_gt_, select, ...}` construct that embeds the value as a General Translation variable marker.

```python
from gt_flask import declare_var  # or: from gt_fastapi import declare_var, or: from gt_i18n import declare_var

t(f"Signed in as {declare_var(email, name='email')}")
```

Signature:

```python
declare_var(
    variable: str | int | float | bool | None,
    *,
    name: str | None = None,
) -> str
```

Re-exported from `generaltranslation.static` by `gt_i18n` and the framework packages.

## How it works [#how-it-works]

* **Value formatting.** `None` becomes an empty string, `bool` becomes `"true"`/`"false"`, and other values are stringified; the result is sanitised.
* **Marker construction.** It returns `{_gt_, select, other {value}}`, optionally with a `_gt_var_name {name}` clause when `name` is given.
* **Runtime vs. build time.** Use it for runtime values; for a value with a finite set of build-time outcomes, use [`derive`](/docs/python/reference/functions/derive). Recover embedded values with [`decode_vars`](/docs/python/reference/functions/decode-vars).

## Parameters [#parameters]

| Parameter               | Description                                        | Type                                  | Optional | Default |
| ----------------------- | -------------------------------------------------- | ------------------------------------- | -------- | ------- |
| [`variable`](#variable) | The value to embed as a non-translatable variable. | `str \| int \| float \| bool \| None` | No       | —       |
| [`name`](#name)         | Keyword-only human-readable variable name.         | `str`                                 | Yes      | `None`  |

### `variable` [#variable]

**Type** `str | int | float | bool | None` · **Required**

The value to embed. `None` renders as an empty string; booleans render in lowercase.

### `name` [#name]

**Type** `str` · **Optional** · **Default** `None`

A keyword-only human-readable label for the variable, added as a `_gt_var_name` clause when provided.

## Returns [#returns]

**Type** `str`

An ICU `{_gt_, select, ...}` construct wrapping the value as a variable marker.

## Example [#example]

```python
from gt_flask import t, declare_var

# Preserve a runtime value inside a translated f-string
message = t(f"{declare_var(name, name='name')} goes home")
```