}
	return nil
}

// walk recursively descends path, calling walkFn.
func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
	if !info.IsDir() {
		return walkFn(path, info, nil)
	}

	names, err := readDirNames(path)
	err1 := walkFn(path, info, err)
	// If err != nil, walk can't walk into this directory.
	// err1 != nil means walkFn want walk to skip this directory or stop walking.

	return false, firstErr
}

// walk recursively descends path, calling walkFn. Copied, with some
// modifications from path/filepath.walk.
func walk(path string, info fs.FileInfo, walkFn filepath.WalkFunc) error {
	if err := walkFn(path, info, nil); err != nil || !info.IsDir() {
		return err
	}

	fis, err := ReadDir(path)
	if err != nil {
		return walkFn(path, info, err)
	}

	for _, fi := range fis {

func (fs *DefaultFs) ReadDir(dirname string) ([]os.DirEntry, error) {
	return os.ReadDir(fs.prefix(dirname))
}

// Walk via filepath.Walk
func (fs *DefaultFs) Walk(root string, walkFn filepath.WalkFunc) error {
	return filepath.Walk(fs.prefix(root), walkFn)
}

// defaultFile implements File using same-named functions from "os"
type defaultFile struct {
	file *os.File
}

// Name via os.File.Name

		count++
		return false
	})
	return count
}

// WalkFn is used when walking the tree. Takes a
// key and value, returning if iteration should
// be terminated.
type WalkFn[T any] func(s netip.Prefix, v T) bool

// DepthFirstWalk is used to walk the tree of the corresponding IP family
func (t *Tree[T]) DepthFirstWalk(isIPv6 bool, fn WalkFn[T]) {
	if isIPv6 {
		recursiveWalk(t.rootV6, fn)
	}

	// from "os"
	ReadFile(filename string) ([]byte, error)
	TempDir(dir, prefix string) (string, error)
	TempFile(dir, prefix string) (File, error)
	ReadDir(dirname string) ([]os.DirEntry, error)
	Walk(root string, walkFn filepath.WalkFunc) error
}

// File is an interface that we can use to mock various filesystem operations typically
// accessed through the File object from the "os" package
type File interface {

func listStdPkgs(goroot string) ([]string, error) {
	// Based on cmd/go's matchPackages function.
	var pkgs []string

	src := filepath.Join(goroot, "src") + string(filepath.Separator)
	walkFn := func(path string, d fs.DirEntry, err error) error {
		if err != nil || !d.IsDir() || path == src {
			return nil
		}

		base := filepath.Base(path)

	walker := func(path string) error {
		if strings.HasSuffix(path, "foo2") {
			sawFoo2 = true
		}
		if strings.HasSuffix(path, "foo1") {
			return filepath.SkipDir
		}
		return nil
	}
	walkFn := func(path string, _ fs.FileInfo, _ error) error { return walker(path) }
	walkDirFn := func(path string, _ fs.DirEntry, _ error) error { return walker(path) }

			var got []string

			err := Walk(tc.dir, func(path string, info fs.FileInfo, err error) error {
				t.Logf("walk %q", path)
				got = append(got, path)
				if err != nil {
					t.Errorf("walkfn: got non nil err argument: %v, want nil err argument", err)
				}
				return nil
			})
			if err != nil {
				t.Errorf("Walk: got error %q, want nil", err)
			}

=== "Python 3.10+"

    ```Python hl_lines="1"
    {!> ../../../docs_src/python_types/tutorial008b_py310.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="1  4"

// Submitted by Shante Adam <******@****.***>
bounty-full.com
alpha.bounty-full.com
beta.bounty-full.com

// Small Technology Foundation : https://small-tech.org
// Submitted by Aral Balkan <******@****.***>
small-web.org

// Smoove.io : https://www.smoove.io/
// Submitted by Dan Kozak <******@****.***>
vp4.me

// Snowflake Inc : https://www.snowflake.com/