from fastapi import BackgroundTasks, Depends, FastAPI

app = FastAPI()


def write_log(message: str):
    with open("log.txt", mode="a") as log:
        log.write(message)


def get_query(background_tasks: BackgroundTasks, q: str | None = None):
    if q:
        message = f"found query: {q}\n"
        background_tasks.add_task(write_log, message)
    return q


@app.post("/send-notification/{email}")

            "type": "value_error.missing",
        }
    ]
}


@needs_py39
def test_post_files(tmp_path, app: FastAPI):
    path = tmp_path / "test.txt"
    path.write_bytes(b"<file content>")
    path2 = tmp_path / "test2.txt"
    path2.write_bytes(b"<file content2>")

    client = TestClient(app)
    with path.open("rb") as file, path2.open("rb") as file2:
        response = client.post(
            "/files/",

                    "type": "value_error.missing",
                }
            ]
        }
    )


def test_post_file(tmp_path):
    path = tmp_path / "test.txt"
    path.write_bytes(b"<file content>")

    client = TestClient(app)
    with path.open("rb") as file:
        response = client.post("/files/", files={"file": file})
    assert response.status_code == 200, response.text

<span style="color: green;">INFO</span>:     Application startup complete.
```

</div>

It is **HIGHLY encouraged** that you write or copy the code, edit it and run it locally.

Using it in your editor is what really shows you the benefits of FastAPI, seeing how little code you have to write, all the type checks, autocompletion, etc.

---

## Install FastAPI

The first step is to install FastAPI.

            ]
        }
    )


@needs_py39
def test_post_files_and_token(tmp_path, app: FastAPI):
    patha = tmp_path / "test.txt"
    pathb = tmp_path / "testb.txt"
    patha.write_text("<file content>")
    pathb.write_text("<file b content>")

    client = TestClient(app)
    with patha.open("rb") as filea, pathb.open("rb") as fileb:
        response = client.post(
            "/files/",

client = TestClient(app)


def test_get(tmp_path: Path):
    file_path: Path = tmp_path / "large-video-file.mp4"
    tutorial009.some_file_path = str(file_path)
    test_content = b"Fake video bytes"
    file_path.write_bytes(test_content)
    response = client.get("/")

client = TestClient(app)


def test_get(tmp_path: Path):
    file_path: Path = tmp_path / "large-video-file.mp4"
    tutorial009b.some_file_path = str(file_path)
    test_content = b"Fake video bytes"
    file_path.write_bytes(test_content)
    response = client.get("/")

    if new_path.exists():
        typer.echo(f"The language was already created: {lang}")
        raise typer.Abort()
    new_path.mkdir()
    new_config_path: Path = Path(new_path) / mkdocs_name
    new_config_path.write_text("INHERIT: ../en/mkdocs.yml\n", encoding="utf-8")
    new_config_docs_path: Path = new_path / "docs"
    new_config_docs_path.mkdir()
    en_index_path: Path = en_docs_path / "docs" / "index.md"

**FastAPI** calls the `CommonQueryParams` class. This creates an "instance" of that class and the instance will be passed as the parameter `commons` to your function.

## Type annotation vs `Depends`

Notice how we write `CommonQueryParams` twice in the above code:

=== "Python 3.8+"

    ```Python
    commons: Annotated[CommonQueryParams, Depends(CommonQueryParams)]
    ```

=== "Python 3.8+ non-Annotated"

    assert response.json() == {"message": "No upload file sent"}


@needs_py310
def test_post_file(tmp_path: Path, client: TestClient):
    path = tmp_path / "test.txt"
    path.write_bytes(b"<file content>")

    with path.open("rb") as file:
        response = client.post("/files/", files={"file": file})
    assert response.status_code == 200, response.text
    assert response.json() == {"file_size": 14}