The **server** program (for example **Uvicorn** via **FastAPI CLI**) is capable of interpreting these headers, and then passing that information to your application.

But for security, as the server doesn't know it is behind a trusted proxy, it won't interpret those headers.

/// note | Technical Details

* `https://www.googleapis.com/auth/drive` is used by Google.

/// info

In OAuth2 a "scope" is just a string that declares a specific permission required.

It doesn't matter if it has other characters like `:` or if it is a URL.

Those details are implementation specific.

For OAuth2 they are just strings.

///

## Global view { #global-view }

# HTTP Basic Auth { #http-basic-auth }

For the simplest cases, you can use HTTP Basic Auth.

In HTTP Basic Auth, the application expects a header that contains a username and a password.

If it doesn't receive it, it returns an HTTP 401 "Unauthorized" error.

And returns a header `WWW-Authenticate` with a value of `Basic`, and an optional `realm` parameter.

That tells the browser to show the integrated prompt for a username and password.

        DirFileEntryEnumIterator2 it = new DirFileEntryEnumIterator2(tree, parent, wildcard, (ResourceNameFilter) null, 0);

        // Assert: first page
        assertTrue(it.hasNext(), "Iterator should have first element");
        assertSame(fe1, it.next(), "First element must match first page");
        assertTrue(it.hasNext(), "Iterator should have second element");
        assertSame(fe2, it.next(), "Second element must match first page");

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.

You can think of it as a *path operation function* without the "decorator" (without the `@app.get("/some-path")`).

And it can return anything you want.

In this case, this dependency expects:

* An optional query parameter `q` that is a `str`.

        val topLevelFunctionalTests =
            topLevelCoverage
                .map { FunctionalTest(model, it.asConfigurationId(model), it.asName(), it.asName(), it, stage = stage) }
        topLevelFunctionalTests.forEach(this::buildType)

        val functionalTestProjects =
            allCoverage.map { testCoverage ->
                FunctionalTestProject(
                    model,

But all this functionality of using asynchronous code with `async` and `await` is many times summarized as using "coroutines". It is comparable to the main key feature of Go, the "Goroutines".

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[13] *}

Let's focus on the parameters declared:

* Even though this function is a dependency ("dependable") itself, it also declares another dependency (it "depends" on something else).
    * It depends on the `query_extractor`, and assigns the value returned by it to the parameter `q`.

You can return it directly.

It accepts the following parameters:

* `content` - A `str` or `bytes`.
* `status_code` - An `int` HTTP status code.
* `headers` - A `dict` of strings.
* `media_type` - A `str` giving the media type. E.g. `"text/html"`.

The `lifespan` parameter of the `FastAPI` app takes an **async context manager**, so we can pass our new `lifespan` async context manager to it.

{* ../../docs_src/events/tutorial003.py hl[22] *}

## Alternative Events (deprecated) { #alternative-events-deprecated }

/// warning