# Entornos Virtuales

Cuando trabajas en proyectos de Python probablemente deberías usar un **entorno virtual** (o un mecanismo similar) para aislar los paquetes que instalas para cada proyecto.

/// info | Información

Si ya sabes sobre entornos virtuales, cómo crearlos y usarlos, podrías querer saltar esta sección. 🤓

///

/// tip | Consejo

Un **entorno virtual** es diferente de una **variable de entorno**.

        <directory>src</directory>
      </resource>
      <!-- src-super is copied to guava-gwt-sources (so that we can strip its @Nullable annotations), so we don't need to list it here. We may want to arrange something similar for test-super someday. -->
      <!-- TODO(cpovirk): Why do we have separate src and src-super directories, anyway? -->
      <resource>
        <directory>${project.build.directory}/guava-gwt-sources</directory>

It would probably all start by you **acquiring** some **domain name**. Then, you would configure it in a DNS server (possibly your same cloud provider).

You would probably get a cloud server (a virtual machine) or something similar, and it would have a <abbr title="That doesn't change">fixed</abbr> **public IP address**.

In the DNS server(s) you would configure a record (an "`A record`") to point **your domain** to the public **IP address of your server**.

@GwtCompatible
public interface Table<
    R extends @Nullable Object, C extends @Nullable Object, V extends @Nullable Object> {
  // TODO(jlevy): Consider adding methods similar to ConcurrentMap methods.

  // Accessors

  /**
   * Returns {@code true} if the table contains a mapping with the specified row and column keys.
   *
   * @param rowKey key of row to search for

  }

  @J2ktIncompatible
  @GwtIncompatible // reflection
  @AndroidIncompatible // TODO(cpovirk): ClassNotFoundException: com.google.common.base.Function
  // (I suspect that this and the other similar failures happen with ArbitraryInstances proxies.)
  public void testEqualsAndSerializable() throws Exception {
    new ClassSanityTester().forAllPublicStaticMethods(Functions.class).testEqualsAndSerializable();
  }

* The item the client was trying to access doesn't exist.
* etc.

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.

* **No brainfuck**:
    * No new schema definition micro-language to learn.
    * If you know Python types you know how to use Pydantic.
* Plays nicely with your **<abbr title="Integrated Development Environment, similar to a code editor">IDE</abbr>/<abbr title="A program that checks for code errors">linter</abbr>/brain**:

/// tip

Having the return model ensure that a value is always available and always `int` (not `None`) is very useful for the API clients, they can write much simpler code having this certainty.

Also, **automatically generated clients** will have simpler interfaces, so that the developers communicating with your API can have a much better time working with your API. 😎

///

We also declare a special parameter of type `SecurityScopes`, imported from `fastapi.security`.

This `SecurityScopes` class is similar to `Request` (`Request` was used to get the request object directly).

{* ../../docs_src/security/tutorial005_an_py310.py hl[9,106] *}

## Use the `scopes` { #use-the-scopes }

// 500 Internal Server Error.
type BucketMetricsLoaderFn func(context.Context, MetricValues, *metricsCache, []string) error

// JoinBucketLoaders - joins multiple bucket loaders into a single loader,
// similar to `JoinLoaders`.
func JoinBucketLoaders(loaders ...BucketMetricsLoaderFn) BucketMetricsLoaderFn {
	return func(ctx context.Context, m MetricValues, c *metricsCache, b []string) error {
		for _, loader := range loaders {