```Python hl_lines="1  3  7" title="app/main.py"
{!../../docs_src/bigger_applications/app/main.py!}
```

### 🗄 `APIRouter`

🔜 👥 🗄 🎏 🔁 👈 ✔️ `APIRouter`Ⓜ:

```Python hl_lines="5" title="app/main.py"
{!../../docs_src/bigger_applications/app/main.py!}
```

///

## The main `FastAPI` { #the-main-fastapi }

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI` { #import-fastapi }

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

In der Datei `main.py` haben Sie Ihre **FastAPI**-Anwendung:


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


### Testdatei

It has the same fields as `HeroBase`, so it won't include `secret_name`.

Finally, the identity of our heroes is protected! 🥷

It also re-declares `id: int`. By doing this, we are making a **contract** with the API clients, so that they can always expect the `id` to be there and to be an `int` (it will never be `None`).

/// tip

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

En el archivo `main.py` tienes tu aplicación de **FastAPI**:

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

### Archivo de prueba

```Python
callback_url = "https://example.com/api/v1/invoices/events/"
httpx.post(callback_url, json={"description": "Invoice paid", "paid": True})
```

But possibly the most important part of the callback is making sure that your API user (the external developer) implements the *external API* correctly, according to the data that *your API* is going to send in the request body of the callback, etc.

The defaults that will be compiled into a main package
are reported by the command:

{{raw `
	go list -f '{{.DefaultGODEBUG}}' my/main/package
`}}

Only differences from the base Go toolchain defaults are reported.

When testing a package, `//go:debug` lines in the `*_test.go`
files are treated as directives for the test's main package.

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

Здесь файл `main.py` является "точкой входа" в Ваше приложение и содержит инициализацию Вашего приложения **FastAPI**:


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

### Файл тестов

    #     (NotRequired - Default Java:'src/main/java' & 'src/main/resources' CSharp:'source')
    #   o sql2EntityOutputDirectory: source output directory from as a relative path from the application directory
    #     (NotRequired - Default Java:'src/main/java' CSharp:'source')
    #
    #; applicationOutsideSqlMap = map:{
    #    ; ../../app1 = map:{
    #        ; sqlDirectory = src/main/resources

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

📁 `main.py` 👆 ✔️ 👆 **FastAPI** 📱:


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

### 🔬 📁

⤴️ 👆 💪 ✔️ 📁 `test_main.py` ⏮️ 👆 💯. ⚫️ 💪 🖖 🔛 🎏 🐍 📦 (🎏 📁 ⏮️ `__init__.py` 📁):

``` hl_lines="5"
.
├── app
│   ├── __init__.py
│   ├── main.py
│   └── test_main.py
```