# Using Dataclasses { #using-dataclasses }

FastAPI is built on top of **Pydantic**, and I have been showing you how to use Pydantic models to declare requests and responses.

But FastAPI also supports using <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> the same way:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

import java.util.List;

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.services.Request;
import org.apache.maven.api.services.Result;

/**
 * Exception thrown when a batch request operation fails. This exception contains the results
 * of all requests that were attempted, including both successful and failed operations.
 * <p>

    stack.addTearDown(tearDownTwo);

    assertEquals(false, tearDownOne.ran);
    assertEquals(false, tearDownTwo.ran);

    try {
      stack.runTearDown();
      fail("runTearDown should have thrown an exception");
    } catch (RuntimeException expected) {
      assertThat(expected).hasMessageThat().isEqualTo("two");
      assertThat(getOnlyElement(asList(expected.getSuppressed())))
          .hasMessageThat()

    // Valid radix values are Character.MIN_RADIX to Character.MAX_RADIX,
    // inclusive.
    //
    // Note: According to the spec, a NumberFormatException is thrown for a number that is not
    // parseable, but the spec doesn't seem to say which exception is thrown for an invalid radix.
    // In contrast to the JVM, Kotlin native throws an Illegal argument exception in this case
    // (which seems to make more sense).
    try {

class WebSocketWriterTest {
  private val data = Buffer()
  private val random = Random(0)

  /**
   * Check all data as verified inside of the test. We do this in an AfterEachCallback so that
   * exceptions thrown from the test do not cause this check to fail.
   */
  @RegisterExtension
  val noDataLeftBehind =
    AfterEachCallback { context: ExtensionContext ->
      if (context.executionException.isPresent) return@AfterEachCallback

      else -> Log.DEBUG
    }

object AndroidLogHandler : Handler() {
  override fun publish(record: LogRecord) {
    androidLog(record.loggerName, record.androidLevel, record.message, record.thrown)
  }

  override fun flush() {
  }

  override fun close() {
  }
}

@SuppressSignatureCheck
object AndroidLog {
  private const val MAX_LOG_LENGTH = 4000

import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.annotations.Nullable;

/**
 * Describes a problem that was encountered during project building. A problem can either be an exception that was
 * thrown or a simple string message. In addition, a problem carries a hint about its source.
 *
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface BuilderProblem {

    /**

    Assert.assertEquals("", escaper.escape(""));
    // Assert that escapers throw null pointer exceptions.
    try {
      escaper.escape((String) null);
      Assert.fail("exception not thrown when escaping a null string");
    } catch (NullPointerException e) {
      // pass
    }
  }

  /**
   * Asserts that an escaper escapes the given character into the expected string.
   *

    Assert.assertEquals("", escaper.escape(""));
    // Assert that escapers throw null pointer exceptions.
    try {
      escaper.escape((String) null);
      Assert.fail("exception not thrown when escaping a null string");
    } catch (NullPointerException e) {
      // pass
    }
  }

  /**
   * Asserts that an escaper escapes the given character into the expected string.
   *

        assertTrue(zebra.compareTo(greek) < 0);
    }

    /**
     * Test <a href="https://issues.apache.org/jira/browse/MNG-5568">MNG-5568</a> edge case
     * which was showing transitive inconsistency: since A &gt; B and B &gt; C then we should have A &gt; C
     * otherwise sorting a list of ComparableVersions() will in some cases throw runtime exception;