# Bigger Applications - Multiple Files { #bigger-applications-multiple-files }

If you are building an application or a web API, it's rarely the case that you can put everything in a single file.

**FastAPI** provides a convenience tool to structure your application while keeping all the flexibility.

/// info

If you come from Flask, this would be the equivalent of Flask's Blueprints.

///

## An example file structure { #an-example-file-structure }

### Top-level application { #top-level-application }

First, create the main, top-level, **FastAPI** application, and its *path operations*:

{* ../../docs_src/sub_applications/tutorial001.py hl[3, 6:8] *}

### Sub-application { #sub-application }

Then, create your sub-application, and its *path operations*.

<img src="https://fastapi.tiangolo.com//img/tutorial/sub-applications/image01.png">

다음으로, <a href="http://127.0.0.1:8000/subapi/docs" class="external-link" target="_blank">http://127.0.0.1:8000/subapi/docs</a>에서 하위 응용프로그램의 문서를 여십시오.

하위 경로 접두사 `/subapi` 아래에 선언된 *경로 동작* 을 포함하는, 하위 응용프로그램에 대한 자동 API 문서를 확인할 수 있습니다:

<img src="https://fastapi.tiangolo.com//img/tutorial/sub-applications/image02.png">

* 📤 📁 `app/internal/` ⏮️ ➕1️⃣ 📁 `__init__.py`, ⚫️ ➕1️⃣ "🐍 📦": `app.internal`.
*  & 📁 `app/internal/admin.py` ➕1️⃣ 🔁: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

🎏 📁 📊 ⏮️ 🏤:

```
.
├── app                  # "app" is a Python package
│   ├── __init__.py      # this file makes "app" a "Python package"

* Y el archivo `app/internal/admin.py` es otro submódulo: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

La misma estructura de archivos con comentarios:

```
.
├── app                  # "app" es un paquete de Python

* E o arquivo `app/internal/admin.py` é outro submódulo: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

A mesma estrutura de arquivos com comentários:

```
.
├── app                  # "app" é um pacote Python
│   ├── __init__.py      # este arquivo torna "app" um "pacote Python"

* Und die Datei `app/internal/admin.py` ist ein weiteres Submodul: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

Die gleiche Dateistruktur mit Kommentaren:

```
.
├── app                  # „app“ ist ein Python-Package
│   ├── __init__.py      # diese Datei macht „app“ zu einem „Python-Package“

* Подкаталог `app/internal/`, содержащий файл `__init__.py`, является ещё одним суб-пакетом: `app.internal`.
* А файл `app/internal/admin.py` является ещё одним суб-модулем: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

Та же самая файловая структура приложения, но с комментариями:

```
.
├── app                  # "app" пакет
│   ├── __init__.py      # этот файл превращает "app" в "Python-пакет"

For some types of applications you might want to add dependencies to the whole application.

Similar to the way you can [add `dependencies` to the *path operation decorators*](dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, you can add them to the `FastAPI` application.

In that case, they will be applied to all the *path operations* in the application:

# Including WSGI - Flask, Django, others { #including-wsgi-flask-django-others }

You can mount WSGI applications as you saw with [Sub Applications - Mounts](sub-applications.md){.internal-link target=_blank}, [Behind a Proxy](behind-a-proxy.md){.internal-link target=_blank}.

For that, you can use the `WSGIMiddleware` and use it to wrap your WSGI application, for example, Flask, Django, etc.

## Using `WSGIMiddleware` { #using-wsgimiddleware }