}
	if _, err := buf.Peek(1); err != io.EOF {
		t.Fatalf("want EOF got %v", err)
	}

	// Test for issue 3022, not exposing a reader's error on a successful Peek.
	buf = NewReaderSize(dataAndEOFReader("abcd"), 32)
	if s, err := buf.Peek(2); string(s) != "ab" || err != nil {
		t.Errorf(`Peek(2) on "abcd", EOF = %q, %v; want "ab", nil`, string(s), err)
	}
	if s, err := buf.Peek(4); string(s) != "abcd" || err != nil {

**FastAPI** is helemaal gebaseerd op deze type hints, ze geven veel voordelen.

Maar zelfs als je **FastAPI** nooit gebruikt, heb je er baat bij om er iets over te leren.

/// note

Als je een Python expert bent en alles al weet over type hints, sla dan dit hoofdstuk over.

///

## Motivatie

Laten we beginnen met een eenvoudig voorbeeld:

```Python
{!../../docs_src/python_types/tutorial001.py!}
```

      STRONG_ACCESS,
      STRONG_WRITE,
      STRONG_ACCESS_WRITE,
      WEAK,
      WEAK_ACCESS,
      WEAK_WRITE,
      WEAK_ACCESS_WRITE,
    };

    static EntryFactory getFactory(
        Strength keyStrength, boolean usesAccessQueue, boolean usesWriteQueue) {
      int flags =
          ((keyStrength == Strength.WEAK) ? WEAK_MASK : 0)
              | (usesAccessQueue ? ACCESS_MASK : 0)

import com.google.common.annotations.VisibleForTesting;
import com.google.common.math.IntMath;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
import java.util.AbstractQueue;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() middle element multiple times", "B", peekingIterator.peek());
    assertEquals(

		{seek: io.SeekCurrent, off: 1, wantpos: 1<<33 + 1, readerr: io.EOF},
		{seek: io.SeekStart, n: 5, want: "01234"},
		{seek: io.SeekCurrent, n: 5, want: "56789"},
		{seek: io.SeekEnd, off: -1, n: 1, wantpos: 9, want: "9"},
	}

	for i, tt := range tests {
		pos, err := r.Seek(tt.off, tt.seek)
		if err == nil && tt.seekerr != "" {
			t.Errorf("%d. want seek error %q", i, tt.seekerr)
			continue
		}

import com.google.common.annotations.VisibleForTesting;
import com.google.common.math.IntMath;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
import java.util.AbstractQueue;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() middle element multiple times", "B", peekingIterator.peek());
    assertEquals(

   *
   * <p>Calls to {@code peek()} should not change the state of the iteration, except that it
   * <i>may</i> prevent removal of the most recent element via {@link #remove()}.
   *
   * @throws NoSuchElementException if the iteration has no more elements according to {@link
   *     #hasNext()}
   */
  @ParametricNullness
  E peek();

  /**
   * {@inheritDoc}
   *

Je hoeft niet langer de verkeerde keys in te typen, op en neer te gaan tussen de documentatie, of heen en weer te scrollen om te checken of je `username` of toch `user_name` had gebruikt.

### Kort