For example:

{* ../../docs_src/additional_responses/tutorial004.py hl[13:17,26] *}

## More information about OpenAPI responses { #more-information-about-openapi-responses }

To see what exactly you can include in the responses, you can check these sections in the OpenAPI specification:

<img src="/img/tutorial/security/image02.png">

/// note

It doesn't matter what you type in the form, it won't work yet. But we'll get there.

///

This is of course not the frontend for the final users, but it's a great automatic tool to document interactively all your API.

It can be used by the frontend team (that can also be yourself).

# Custom Response Classes - File, HTML, Redirect, Streaming, etc.

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,

In these cases, you would normally return an **HTTP status code** in the range of **400** (from 400 to 499).

This is similar to the 200 HTTP status codes (from 200 to 299). Those "200" status codes mean that somehow there was a "success" in the request.

The status codes in the 400 range mean that there was an error from the client.

Remember all those **"404 Not Found"** errors (and jokes)?

## Use `HTTPException` { #use-httpexception }

 *   <li>{@linkplain State#RUNNING RUNNING} -&gt;
 *   <li>{@linkplain State#STOPPING STOPPING} -&gt;
 *   <li>{@linkplain State#TERMINATED TERMINATED}
 * </ul>
 *
 * <p>There are deviations from this if there are failures or if {@link Service#stopAsync} is called
 * before the {@link Service} reaches the {@linkplain State#RUNNING RUNNING} state. The set of legal

func (p *parallelReader) Done() {
	if p.stashBuffer != nil {
		globalBytePoolCap.Load().Put(p.stashBuffer)
		p.stashBuffer = nil
	}
}

// preferReaders can mark readers as preferred.
// These will be chosen before others.
func (p *parallelReader) preferReaders(prefer []bool) {
	if len(prefer) != len(p.orgReaders) {
		return
	}
	// Copy so we don't change our input.
	tmp := make([]io.ReaderAt, len(p.orgReaders))

    }
  }

  // TODO(lukes): Investigate using a @Contended annotation on these fields once one is available.

  /*
   * The following fields are package-private, even though we intend never to use them outside this
   * file. If they were instead private, then we wouldn't be able to access them reflectively from
   * within VarHandleAtomicHelper and AtomicReferenceFieldUpdaterAtomicHelper.
   *

* `DELETE`

...and the more exotic ones:

* `OPTIONS`
* `HEAD`
* `PATCH`
* `TRACE`

In the HTTP protocol, you can communicate to each path using one (or more) of these "methods".

---

When building APIs, you normally use these specific HTTP methods to perform a specific action.

Normally you use:

* `POST`: to create data.
* `GET`: to read data.
* `PUT`: to update data.

 * itself is reclaimable. <i>Weak</i> means that locks/semaphores are created lazily, and they are
 * allowed to be reclaimed if nobody is holding on to them. This is useful, for example, if one
 * wants to create a {@code Striped<Lock>} of many locks, but worries that in most cases only a
 * small portion of these would be in use.
 *
 * <p>Prior to this class, one might be tempted to use {@code Map<K, Lock>}, where {@code K}

  // null pointer. If `table[h] == 0` that means there are no keys in the map whose short hash is h.
  // If the `next` bits in `entries[i]` are 0 that means there are no further entries for the given
  // short hash. But 0 is also a valid index in `entries`, so we add 1 to these indices before
  // putting them in `table` or in `next` bits, and subtract 1 again when we need an index value.
  //