## External Courses

Although the [Tutorial - User Guide](../tutorial/index.md){.internal-link target=_blank} and this **Advanced User Guide** are written as a guided tutorial (like a book) and should be enough for you to **learn FastAPI**, you might want to complement it with additional courses.

Or it might be the case that you just prefer to take other courses because they adapt better to your learning style.

// overuse of Clone can make programs use more memory.
// Clone should typically be used only rarely, and only when
// profiling indicates that it is needed.
// For strings of length zero the string "" will be returned
// and no allocation is made.
func Clone(s string) string {
	return stringslite.Clone(s)

For details about who's involved and how Kubernetes plays a role,
read the CNCF [announcement].

----

## To start using K8s

See our documentation on [kubernetes.io].

Take a free course on [Scalable Microservices with Kubernetes].

To use Kubernetes code as a library in other applications, see the [list of published components](https://git.k8s.io/kubernetes/staging/README.md).

// best approach was for Go to raise the limit unconditionally for itself,
// and then leave old software to set the limit back as needed.
// Code that really wants Go to leave the limit alone can set the hard limit,
// which Go of course has no choice but to respect.
func init() {
	var lim Rlimit
	if err := Getrlimit(RLIMIT_NOFILE, &lim); err == nil && lim.Cur != lim.Max {
		origRlimitNofile.Store(&lim)
		nlim := lim
		nlim.Cur = nlim.Max

          @ParametricNullness E key,
          List<? extends E> list,
          int foundIndex) {
        // Of course, we have to use binary search to find the precise
        // breakpoint...
        int lower = 0;
        int upper = foundIndex;
        // Of course, we have to use binary search to find the precise breakpoint...
        // Everything between lower and upper inclusive compares at <= 0.

 */
class MultiReleaseClasspathElementTransformForLegacy extends BaseClasspathElementTransform {
    MultiReleaseClasspathElementTransformForLegacy(File source, ClasspathBuilder classpathBuilder, ClasspathWalker classpathWalker, InstrumentationTypeRegistry typeRegistry, ClassTransform transform) {
        super(source, classpathBuilder, classpathWalker, typeRegistry, transform);
    }

    @Override

          @ParametricNullness E key,
          List<? extends E> list,
          int foundIndex) {
        // Of course, we have to use binary search to find the precise
        // breakpoint...
        int lower = 0;
        int upper = foundIndex;
        // Of course, we have to use binary search to find the precise breakpoint...
        // Everything between lower and upper inclusive compares at <= 0.

  }

  /**
   * The version of this test supplied by {@link MapInterfaceTest} fails for this particular Map
   * implementation, because {@code map.get()} returns a view collection that changes in the course
   * of a call to {@code remove()}. Thus, the expectation doesn't hold that {@code map.remove(x)}
   * returns the same value which {@code map.get(x)} did immediately beforehand.
   */
  @Override
  public void testRemove() {

     * Returns the cache configuration for downloaded resources.
     */
    CacheResourceConfiguration getDownloadedResources();

    /**
     * Configures caching for resources that are created by Gradle during the course of a build.  By default, created
     * resources are removed after 7 days of not being used.
     */
    void createdResources(Action<? super CacheResourceConfiguration> cacheConfiguration);

    /**

# Body - Multiple Parameters

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

And you can also declare body parameters as optional, by setting the default to `None`:

=== "Python 3.10+"