- url: https://platform.sh/try-it-now/?utm_source=fastapi-signup&utm_medium=banner&utm_campaign=FastAPI-signup-June-2023
    title: "Build, run and scale your apps on a modern, reliable, and secure PaaS."
    img: https://fastapi.tiangolo.com/img/sponsors/platform-sh.png
  - url: https://www.porter.run
    title: Deploy FastAPI on AWS with a few clicks
    img: https://fastapi.tiangolo.com/img/sponsors/porter.png

        <img class="sponsor-image" src="/img/sponsors/cryptapi-banner.svg" />
      </a>
    </div>
    <div class="item">
      <a title="Build, run and scale your apps on a modern, reliable, and secure PaaS." style="display: block; position: relative;" href="https://platform.sh/try-it-now/?utm_source=fastapi-signup&utm_medium=banner&utm_campaign=FastAPI-signup-June-2023" target="_blank">

        ),
    ] = None,
    title: Annotated[
        Optional[str],
        Doc(
            """
            Human-readable title.
            """
        ),
    ] = None,
    description: Annotated[
        Optional[str],
        Doc(
            """
            Human-readable description.
            """
        ),
    ] = None,
    gt: Annotated[
        Optional[float],
        Doc(

* Dependency Injection system.

It doesn't use a data validation, serialization and documentation third-party library like Pydantic, it has its own. So, these data type definitions would not be reusable as easily.

It requires a little bit more verbose configurations. And as it is based on WSGI (instead of ASGI), it is not designed to take advantage of the high performance provided by tools like Uvicorn, Starlette and Sanic.

<a href="https://platform.sh/try-it-now/?utm_source=fastapi-signup&utm_medium=banner&utm_campaign=FastAPI-signup-June-2023" target="_blank" title="Build, run and scale your apps on a modern, reliable, and secure PaaS."><img src="https://fastapi.tiangolo.com/img/sponsors/platform-sh.png"></a>

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    },
    auto_error=False,
)


class User(BaseModel):
    username: str


def get_current_user(oauth_header: Optional[str] = Security(reusable_oauth2)):
    if oauth_header is None:

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

from fastapi import Depends, FastAPI, Security
from fastapi.security import OAuth2, OAuth2PasswordRequestFormStrict
from fastapi.testclient import TestClient
from pydantic import BaseModel

app = FastAPI()

reusable_oauth2 = OAuth2(
    flows={
        "password": {
            "tokenUrl": "token",
            "scopes": {"read:users": "Read the users", "write:users": "Create users"},
        }
    }
)

# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
# IN THE SOFTWARE.

* API keys in:
    * Headers.
    * Query parameters.
    * Cookies, etc.

Plus all the security features from Starlette (including **session cookies**).

All built as reusable tools and components that are easy to integrate with your systems, data stores, relational and NoSQL databases, etc.

### Dependency Injection