`FastAPI` aslında `Starlette`'nin bir sub-class'ı. Eğer Starlette'nin nasıl kullanılacağını biliyor isen, çoğu işlevini aynı şekilde yapıyor.

**FastAPI** ile beraber **Starlette**'nin bütün özelliklerine de sahip olacaksınız (FastAPI aslında Starlette'nin steroid basmış hali):

```

#### `RequestValidationError` vs `ValidationError`

!!! warning
    These are technical details that you might skip if it's not important for you now.

`RequestValidationError` is a sub-class of Pydantic's <a href="https://docs.pydantic.dev/latest/concepts/models/#error-handling" class="external-link" target="_blank">`ValidationError`</a>.

    from docs_src.security.tutorial005_an_py39 import create_access_token

    access_token = create_access_token(data={"data": "foo"})
    assert access_token


@needs_py39
def test_token_no_sub(client: TestClient):
    response = client.get(
        "/users/me",
        headers={
            "Authorization": "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJkYXRhIjoiZm9vIn0.9ynBhuYb4e6aW3oJr_K_TBgwcMTDpRToQIE25L57rOE"

    from docs_src.security.tutorial005_py310 import create_access_token

    access_token = create_access_token(data={"data": "foo"})
    assert access_token


@needs_py310
def test_token_no_sub(client: TestClient):
    response = client.get(
        "/users/me",
        headers={
            "Authorization": "Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJkYXRhIjoiZm9vIn0.9ynBhuYb4e6aW3oJr_K_TBgwcMTDpRToQIE25L57rOE"

If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a *path operation function*. Including sub-dependencies.

That also applies to callables with no parameters at all. The same as it would be for *path operation functions* with no parameters.

        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_data = TokenData(username=username)
    except JWTError:
        raise credentials_exception

        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)

        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)

        headers={"WWW-Authenticate": authenticate_value},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:
            raise credentials_exception
        token_scopes = payload.get("scopes", [])
        token_data = TokenData(scopes=token_scopes, username=username)

!!! tip
    There's an equivalent article using Peewee here in the docs.

## File structure

For these examples, let's say you have a directory named `my_super_project` that contains a sub-directory called `sql_app` with a structure like this:

```
.
└── sql_app
    ├── __init__.py
    ├── crud.py
    ├── database.py
    ├── main.py
    ├── models.py
    └── schemas.py
```