# Concurrencia y async / await

Detalles sobre la sintaxis `async def` para *path operation functions* y algunos antecedentes sobre el código asíncrono, la concurrencia y el paralelismo.

## ¿Con prisa?

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

Si estás usando paquetes de terceros que te dicen que los llames con `await`, como:

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

@app.get("/items/{item_id}")
async def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

**Nota**:

Si no lo sabes, revisa la sección _"¿Con prisa?"_ sobre <a href="https://fastapi.tiangolo.com/async/#in-a-hurry" target="_blank">`async` y `await` en la documentación</a>.

</details>

### Córrelo

Corre el servidor con:

<div class="termy">

    hashFunctions[0] = Murmur3_128HashFunction.GOOD_FAST_HASH_128;
    int seed = GOOD_FAST_HASH_SEED;
    for (int i = 1; i < hashFunctionsNeeded; i++) {
      seed += 1500450271; // a prime; shouldn't matter
      hashFunctions[i] = murmur3_128(seed);
    }
    return new ConcatenatedHashFunction(hashFunctions);
  }

  /**

          | (1 << 29));

  /**
   * Returns {@code true} if {@code n} is a <a
   * href="http://mathworld.wolfram.com/PrimeNumber.html">prime number</a>: an integer <i>greater
   * than one</i> that cannot be factored into a product of <i>smaller</i> positive integers.
   * Returns {@code false} if {@code n} is zero, one, or a composite number (one which <i>can</i> be

    //     ends up at a[d], which in turn ends up at a[2d], and so on until we get back to a[0].
    //     (All indices taken mod n.) If d and n are mutually prime, all elements will have been
    //     moved at that point. Otherwise, we can rotate the cycle a[1], a[1 + d], a[1 + 2d], etc,
    //     then a[2] etc, and so on until we have rotated all elements. There are gcd(d, n) cycles

Usar contenedores de Linux tiene varias ventajas, incluyendo **seguridad**, **replicabilidad**, **simplicidad**, y otras.

/// tip | Consejo

¿Tienes prisa y ya conoces esto? Salta al [`Dockerfile` más abajo 👇](#construir-una-imagen-de-docker-para-fastapi).

///

<details>
<summary>Vista previa del Dockerfile 👀</summary>

```Dockerfile
FROM python:3.9

Si necesitas actualizar una versión o agregar un nuevo paquete, **harías esto de nuevo**.

///

### Instala Paquetes Directamente

Si tienes prisa y no quieres usar un archivo para declarar los requisitos de paquetes de tu proyecto, puedes instalarlos directamente.

/// tip | Consejo

    hashFunctions[0] = Murmur3_128HashFunction.GOOD_FAST_HASH_128;
    int seed = GOOD_FAST_HASH_SEED;
    for (int i = 1; i < hashFunctionsNeeded; i++) {
      seed += 1500450271; // a prime; shouldn't matter
      hashFunctions[i] = murmur3_128(seed);
    }
    return new ConcatenatedHashFunction(hashFunctions);
  }

  /**

SetBytesWithClamping returns nil and an error, and the receiver is unchanged. // // Note that since Scalar values are always reduced modulo the prime order of // the curve, the resulting value will not preserve any of the cofactor-clearing // properties that clamping is meant to provide. It will however work as // expected as long as it is applied to points on the prime order subgroup, like // in Ed25519. In fact, it is lost to history why RFC 8032 adopted the // irrelevant RFC 7748 clamping, but it is now...

	for i := range src {  // Loop over values received from 'src'.
		if i%prime != 0 {
			dst <- i  // Send 'i' to channel 'dst'.
		}
	}
}

// The prime sieve: Daisy-chain filter processes together.
func sieve() {
	ch := make(chan int)  // Create a new channel.
	go generate(ch)       // Start generate() as a subprocess.
	for {
		prime := <-ch
		fmt.Print(prime, "\n")