**FastAPI** is all based on these type hints, they give it many advantages and benefits.

But even if you never use **FastAPI**, you would benefit from learning a bit about them.

/// note

If you are a Python expert, and you already know everything about type hints, skip to the next chapter.

///

## Motivation { #motivation }

Let's start with a simple example:

{* ../../docs_src/python_types/tutorial001_py39.py *}

import com.google.common.base.Suppliers;
import com.google.common.collect.ImmutableList;
import com.google.common.testing.ClassSanityTester;
import com.google.common.util.concurrent.MoreExecutors.Application;
import java.lang.Thread.State;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;

import com.google.common.math.IntMath;
import com.google.common.primitives.Ints;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.math.RoundingMode;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.Semaphore;

import java.security.PermissionCollection;
import java.security.Permissions;
import java.security.Policy;
import java.security.ProtectionDomain;
import java.security.SecurityPermission;
import java.util.Date;
import java.util.NoSuchElementException;
import java.util.PropertyPermission;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.Callable;
import java.util.concurrent.CountDownLatch;

package org.codelibs.fess.crawler.client.ftp;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.URI;
import java.net.URISyntaxException;
import java.time.Duration;
import java.util.HashSet;
import java.util.Queue;

import static org.mockito.ArgumentMatchers.anyInt;
import static org.mockito.Mockito.doNothing;
import static org.mockito.Mockito.doThrow;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.times;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

import java.io.IOException;
import java.net.InetAddress;
import java.net.UnknownHostException;

 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
package jcifs;

import java.net.InetAddress;
import java.security.SecureRandom;
import java.util.List;
import java.util.TimeZone;

/**
 *
 *
 * Implementors of this interface should extend {@link jcifs.config.BaseConfiguration} or

 */
package org.apache.maven.classrealm;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import java.io.File;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.Random;
import java.util.Set;
import java.util.TreeMap;

 * limitations under the License.
 */

package gradlebuild.binarycompatibility

import me.champeau.gradle.japicmp.report.PostProcessViolationsRule
import me.champeau.gradle.japicmp.report.SetupRule
import me.champeau.gradle.japicmp.report.ViolationCheckContext
import me.champeau.gradle.japicmp.report.ViolationCheckContextWithViolations

import java.io.File

 */
package jcifs.config;

import java.io.UnsupportedEncodingException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.TimeZone;