OAuth2 is a specification that defines several ways to handle authentication and authorization.

It is quite an extensive specification and covers several complex use cases.

It includes ways to authenticate using a "third party".

That's what all the systems with "login with Facebook, Google, X (Twitter), GitHub" use underneath.

### OAuth 1 { #oauth-1 }

	// and don't process the If-Modified-Since header.
	if objInfo.ModTime.IsZero() || objInfo.ModTime.Equal(time.Unix(0, 0)) {
		return false
	}

	// Check if the part number is correct.
	if opts.PartNumber > 1 {
		partFound := false
		for _, pi := range objInfo.Parts {
			if pi.Number == opts.PartNumber {
				partFound = true
				break
			}
		}
		if !partFound {

## In a hurry? { #in-a-hurry }

<abbr title="too long; didn't read"><strong>TL;DR:</strong></abbr>

If you are using third party libraries that tell you to call them with `await`, like:

```Python
results = await some_library()
```

Then, declare your *path operation functions* with `async def` like:

```Python hl_lines="2"
@app.get('/')

import org.slf4j.ILoggerFactory;
import org.slf4j.LoggerFactory;

/**
 * Use an SLF4J {@link ILoggerFactory} as a backing for a Plexus
 * {@link LoggerManager},
 * ignoring Plexus logger API parts that are not classical and probably not really used.
 *
 * @since 3.1
 */
public class Slf4jLoggerManager implements LoggerManager {

    private final ILoggerFactory loggerFactory;

# Using the Request Directly { #using-the-request-directly }

Up to now, you have been declaring the parts of the request that you need with their types.

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

## Pydantic `bytes` { #pydantic-bytes }

Puedes declarar un modelo de Pydantic con campos `bytes`, y luego usar `val_json_bytes` en la configuración del modelo para indicarle que use base64 para validar datos JSON de entrada; como parte de esa validación decodificará el string base64 en bytes.

{* ../../docs_src/json_base64_bytes/tutorial001_py310.py ln[1:9,29:35] hl[9] *}

Si revisas `/docs`, verás que el campo `data` espera bytes codificados en base64:

Hallo wieder
////

### Headings

Every Markdown heading in the English text (all levels) ends with a part inside curly brackets. This part denotes the hash of this heading, which is used in links to this heading. In translations, translate the heading, but do not translate this hash part, so that links do not break.

Examples of how to translate a heading:

Source (English):

```

### The callback path expression { #the-callback-path-expression }

The callback *path* can have an [OpenAPI 3 expression](https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.1.0.md#key-expression) that can contain parts of the original request sent to *your API*.

In this case, it's the `str`:

package org.apache.maven.cling.logging;

import org.apache.maven.logging.ProjectBuildLogAppender;
import org.codehaus.plexus.logging.Logger;

/**
 * Adapt an SLF4J logger to a Plexus logger, ignoring Plexus logger API parts that are not classical and
 * probably not really used.
 *
 * @since 3.1.0
 */
public class Slf4jLogger implements Logger {

    private final org.slf4j.Logger logger;
    private final String projectId;

	AmzFwdHeaderObjectLockRetainUntil = "x-amz-fwd-header-x-amz-object-lock-retain-until-date"
	AmzFwdHeaderMPPartsCount          = "x-amz-fwd-header-x-amz-mp-parts-count"
	AmzFwdHeaderReplicationStatus     = "x-amz-fwd-header-x-amz-replication-status"
	AmzFwdHeaderSSE                   = "x-amz-fwd-header-x-amz-server-side-encryption"