<div class="termy">

```console
// Here we don't set the env var yet
$ python main.py

// As we didn't set the env var, we get the default value

Hello World from Python

// But if we create an environment variable first
$ export MY_NAME="Wade Wilson"

// And then call the program again
$ python main.py

// Now it can read the environment variable

Hello Wade Wilson from Python
```

## How it looks { #how-it-looks }

Let's first just use the code and see how it works, and then we'll come back to understand what's happening.

## Create `main.py` { #create-main-py }

Copy the example in a file `main.py`:

{* ../../docs_src/security/tutorial001_an_py39.py *}

## Run it { #run-it }

/// info

## Call `uvicorn` { #call-uvicorn }

In your FastAPI application, import and run `uvicorn` directly:

{* ../../docs_src/debugging/tutorial001.py hl[1,15] *}

### About `__name__ == "__main__"` { #about-name-main }

The main purpose of the `__name__ == "__main__"` is to have some code that is executed when your file is called with:

<div class="termy">

```console
$ python myapp.py
```

</div>

```
.
├── app
│   ├── __init__.py
│   └── main.py
```

In the file `main.py` you have your **FastAPI** app:


{* ../../docs_src/app_testing/main.py *}

### Testing file { #testing-file }

 * applies first-in-first-out tie-breaking to comparable elements. To use it, you would insert a
 * {@code new FIFOEntry(anEntry)} instead of a plain entry object.
 *
 * <pre>{@code
 * class FIFOEntry<E extends Comparable<? super E>> implements Comparable<FIFOEntry<E>> {
 *   static final AtomicLong seq = new AtomicLong();
 *
 *   final long seqNum;

<div class="termy">

```console
// Aqui ainda não definimos a variável de ambiente
$ python main.py

// Como não definimos a variável de ambiente, obtemos o valor padrão

Hello World from Python

// Mas se criarmos uma variável de ambiente primeiro
$ export MY_NAME="Wade Wilson"

// E então chamar o programa novamente
$ python main.py

// Agora ele pode ler a variável de ambiente

Hello Wade Wilson from Python
```

import java.util.concurrent.ThreadFactory;
import java.util.concurrent.atomic.AtomicBoolean;
import org.jspecify.annotations.Nullable;

/**
 * Utilities necessary for working with libraries that supply plain {@link Future} instances. Note
 * that, whenever possible, it is strongly preferred to modify those libraries to return {@code
 * ListenableFuture} directly.
 *

Para rodar qualquer um dos exemplos, copie o codigo para um arquivo `main.py`, e inicie o `uvivorn` com:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:solid">main.py</u>

  <span style="background-color:#009485"><font color="#D3D7CF"> FastAPI </font></span>  Starting development server 🚀

   <span style="background-color:#007166"><font color="#D3D7CF"> module </font></span>  🐍 main.py

     <span style="background-color:#007166"><font color="#D3D7CF"> code </font></span>  Importing the FastAPI app object from the module with the
             following code:

        }
    }

    // Test main method with invalid arguments
    public void test_main_invalidArguments() {
        // Cannot directly test main as it calls System.exit
        // Test argument parsing instead
        SuggestCreator.Options options = new SuggestCreator.Options();
        assertNotNull(options);
    }

    // Test main method with valid arguments