## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

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

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

You don't even need to write the body of the function. The `@app.vibe()` decorator does everything for you based on AI vibes:

{* ../../docs_src/vibe/tutorial001_py310.py hl[8:12] *}

## Benefits { #benefits }

By using `@app.vibe()`, you get to enjoy:

This tool will help you to automatically change most of the code that needs to be changed.

After this, you can run the tests and check if everything works. If it does, you are done. 😎

## Pydantic v1 in v2 { #pydantic-v1-in-v2 }

Pydantic v2 includes everything from Pydantic v1 as a submodule `pydantic.v1`. But this is no longer supported in versions above Python 3.13.

It's also possible to declare the list as `"*"` (a "wildcard") to say that all are allowed.

But that will only allow certain types of communication, excluding everything that involves credentials: Cookies, Authorization headers like those used with Bearer Tokens, etc.

So, for everything to work correctly, it's better to specify explicitly the allowed origins.

## Use `CORSMiddleware` { #use-corsmiddleware }

* `.gitignore`: the name of the file where the text should be written

And `*` for Git means "everything". So, it will ignore everything in the `.venv` directory.

That command will create a file `.gitignore` with the content:

```gitignore
*
```

///

## Install Packages { #install-packages }

Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

///

### Create a *path operation* to test it { #create-a-path-operation-to-test-it }

Now, to be able to test that everything works, create a *path operation*:

{* ../../docs_src/custom_docs_ui/tutorial001_py310.py hl[36:38] *}

### Test it { #test-it }

 * is a thin wrapper around {@link InetAddresses} and {@link InternetDomainName}; the unit tests for
 * those classes explore numerous corner cases. The intent here is to confirm that everything is
 * wired up properly.
 *
 * @author Craig Berry
 */
@NullUnmarked
@GwtIncompatible
@J2ktIncompatible
public final class HostSpecifierTest extends TestCase {

3. **Actively collaborate with us.** We commit real time and attention to everything we review. Low-effort submissions—where code is generated, submitted, and abandoned—waste our limited review capacity.

## What contributors can expect from us

          assertEscaping(xmlEscaper, "&#x" + Integer.toHexString(ch).toUpperCase() + ";", ch);
        } else {
          assertUnescaped(xmlEscaper, ch);
        }
      } else {
        // and everything else is replaced with FFFD.
        assertEscaping(xmlEscaper, "\uFFFD", ch);
      }
    }

    // Test _all_ allowed characters (including surrogate values).
    for (char ch = 0x20; ch <= 0xFFFD; ch++) {

No more typing the wrong key names, coming back and forth between docs, or scrolling up and down to find if you finally used `username` or `user_name`.

### Short { #short }

It has sensible **defaults** for everything, with optional configurations everywhere. All the parameters can be fine-tuned to do what you need and to define the API you need.

But by default, it all **"just works"**.

### Validation { #validation }