| # Using Gradio Blocks Like Functions | |
| Tags: TRANSLATION, HUB, SPACES | |
| **Prerequisite**: This Guide builds on the Blocks Introduction. Make sure to [read that guide first](https://gradio.app/blocks-and-event-listeners). | |
| ## Introduction | |
| Did you know that apart from being a full-stack machine learning demo, a Gradio Blocks app is also a regular-old python function!? | |
| This means that if you have a gradio Blocks (or Interface) app called `demo`, you can use `demo` like you would any python function. | |
| So doing something like `output = demo("Hello", "friend")` will run the first event defined in `demo` on the inputs "Hello" and "friend" and store it | |
| in the variable `output`. | |
| If I put you to sleep 🥱, please bear with me! By using apps like functions, you can seamlessly compose Gradio apps. | |
| The following section will show how. | |
| ## Treating Blocks like functions | |
| Let's say we have the following demo that translates english text to german text. | |
| $code_english_translator | |
| I already went ahead and hosted it in Hugging Face spaces at [gradio/english_translator](https://huggingface.co/spaces/gradio/english_translator). | |
| You can see the demo below as well: | |
| $demo_english_translator | |
| Now, let's say you have an app that generates english text, but you wanted to additionally generate german text. | |
| You could either: | |
| 1. Copy the source code of my english-to-german translation and paste it in your app. | |
| 2. Load my english-to-german translation in your app and treat it like a normal python function. | |
| Option 1 technically always works, but it often introduces unwanted complexity. | |
| Option 2 lets you borrow the functionality you want without tightly coupling our apps. | |
| All you have to do is call the `Blocks.load` class method in your source file. | |
| After that, you can use my translation app like a regular python function! | |
| The following code snippet and demo shows how to use `Blocks.load`. | |
| Note that the variable `english_translator` is my english to german app, but its used in `generate_text` like a regular function. | |
| $code_generate_english_german | |
| $demo_generate_english_german | |
| ## How to control which function in the app to use | |
| If the app you are loading defines more than one function, you can specify which function to use | |
| with the `fn_index` and `api_name` parameters. | |
| In the code for our english to german demo, you'll see the following line: | |
| ```python | |
| translate_btn.click(translate, inputs=english, outputs=german, api_name="translate-to-german") | |
| ``` | |
| The `api_name` gives this function a unique name in our app. You can use this name to tell gradio which | |
| function in the upstream space you want to use: | |
| ```python | |
| english_generator(text, api_name="translate-to-german")[0]["generated_text"] | |
| ``` | |
| You can also use the `fn_index` parameter. | |
| Imagine my app also defined an english to spanish translation function. | |
| In order to use it in our text generation app, we would use the following code: | |
| ```python | |
| english_generator(text, fn_index=1)[0]["generated_text"] | |
| ``` | |
| Functions in gradio spaces are zero-indexed, so since the spanish translator would be the second function in my space, | |
| you would use index 1. | |
| ## Parting Remarks | |
| We showed how treating a Blocks app like a regular python helps you compose functionality across different apps. | |
| Any Blocks app can be treated like a function, but a powerful pattern is to `load` an app hosted on | |
| [Hugging Face Spaces](https://huggingface.co/spaces) prior to treating it like a function in your own app. | |
| You can also load models hosted on the [Hugging Face Model Hub](https://huggingface.co/models) - see the [Using Hugging Face Integrations](/using_hugging_face_integrations) guide for an example. | |
| ### Happy building! ⚒️ | |