# Concurrency and async / await { #concurrency-and-async-await }

Details about the `async def` syntax for *path operation functions* and some background about asynchronous code, concurrency, and parallelism.

## 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()
```

func (e stsErrorCodeMap) ToSTSErr(errCode STSErrorCode) STSError {
	apiErr, ok := e[errCode]
	if !ok {
		return e[ErrSTSInternalError]
	}
	return apiErr
}

// error code to STSError structure, these fields carry respective
// descriptions for all the error responses.
var stsErrCodes = stsErrorCodeMap{
	ErrSTSAccessDenied: {
		Code:           "AccessDenied",

      val rule = publicSuffixList.bytes.binarySearch(domainLabelsUtf8Bytes, i)
      if (rule != null) {
        exactMatch = rule
        break
      }
    }

    // In theory, wildcard rules are not restricted to having the wildcard in the leftmost position.
    // In practice, wildcards are always in the leftmost position. For now, this implementation

 * java.util.function.Supplier}, making conversion code necessary only in one direction. At that
 * time, this interface will be officially discouraged.
 *
 * @author Harry Heymann
 * @since 2.0
 */
@GwtCompatible
public interface Supplier<T extends @Nullable Object> {
  /**
   * Retrieves an instance of the appropriate type. The returned object may or may not be a new

You could also define it as a normal function instead of `async def`:

{* ../../docs_src/first_steps/tutorial003_py39.py hl[7] *}

/// note

If you don't know the difference, check the [Async: *"In a hurry?"*](../async.md#in-a-hurry){.internal-link target=_blank}.

///

### Step 5: return the content { #step-5-return-the-content }

{* ../../docs_src/first_steps/tutorial001_py39.py hl[8] *}

      }
      spinCount++;
      if (spinCount > MAX_BUSY_WAIT_SPINS) {
        /*
         * If we have spun a lot, just park ourselves. This will save CPU while we wait for a slow
         * interrupting thread. In theory, interruptTask() should be very fast, but due to
         * InterruptibleChannel and JavaLangAccess.blockedOn(Thread, Interruptible), it isn't

 * class. Similarly, if you know that a given string represents a domain name, use {@link
 * InternetDomainName} rather than this class.
 *
 * @author Craig Berry
 * @since 5.0
 */
@J2ktIncompatible
@GwtIncompatible
public final class HostSpecifier {

  private final String canonicalForm;

  private HostSpecifier(String canonicalForm) {

    * Por ejemplo, `await myfile.seek(0)` iría al inicio del archivo.
    * Esto es especialmente útil si ejecutas `await myfile.read()` una vez y luego necesitas leer el contenido nuevamente.
* `close()`: Cierra el archivo.

Como todos estos métodos son métodos `async`, necesitas "await" para ellos.

Por ejemplo, dentro de una *path operation function* `async` puedes obtener los contenidos con:

```Python

        noMoreExchanges(null)
      }
    }
  }

  /**
   * Prepare for a potential trip through all of this call's network interceptors. This prepares to
   * find an exchange to carry the request.
   *
   * Note that an exchange will not be needed if the request is satisfied by the cache.
   *
   * @param newRoutePlanner true if this is not a retry and new routing can be performed.
   */

Aber schauen wir uns zunächst ein paar kleine Konzepte an.

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

Wenn Ihnen diese Begriffe egal sind und Sie einfach *jetzt* Sicherheit mit Authentifizierung basierend auf Benutzername und Passwort hinzufügen müssen, fahren Sie mit den nächsten Kapiteln fort.

## OAuth2 { #oauth2 }