Add slicing notation to --playlist-items

* Adds support for negative indices and step
* Add `-I` as alias for `--playlist-index`
* Deprecates `--playlist-start`, `--playlist-end`, `--playlist-reverse`, `--no-playlist-reverse`

Closes #2951, Closes #2853

README.md

@@ -427,16 +427,15 @@ ## Geo-restriction:
                                     explicitly provided IP block in CIDR notation
 
 ## Video Selection:
-    --playlist-start NUMBER         Playlist video to start at (default is 1)
-    --playlist-end NUMBER           Playlist video to end at (default is last)
-    --playlist-items ITEM_SPEC      Playlist video items to download. Specify
-                                    indices of the videos in the playlist
-                                    separated by commas like: "--playlist-items
-                                    1,2,5,8" if you want to download videos
-                                    indexed 1, 2, 5, 8 in the playlist. You can
-                                    specify range: "--playlist-items
-                                    1-3,7,10-13", it will download the videos at
-                                    index 1, 2, 3, 7, 10, 11, 12 and 13
+    -I, --playlist-items ITEM_SPEC  Comma seperated playlist_index of the videos
+                                    to download. You can specify a range using
+                                    "[START]:[STOP][:STEP]". For backward
+                                    compatibility, START-STOP is also supported.
+                                    Use negative indices to count from the right
+                                    and negative STEP to download in reverse
+                                    order. Eg: "-I 1:3,7,-5::2" used on a
+                                    playlist of size 15 will download the videos
+                                    at index 1,2,3,7,11,13,15
     --min-filesize SIZE             Do not download any videos smaller than SIZE
                                     (e.g. 50k or 44.6m)
     --max-filesize SIZE             Do not download any videos larger than SIZE
@@ -540,9 +539,6 @@ ## Download Options:
                                     is disabled). May be useful for bypassing
                                     bandwidth throttling imposed by a webserver
                                     (experimental)
-    --playlist-reverse              Download playlist videos in reverse order
-    --no-playlist-reverse           Download playlist videos in default order
-                                    (default)
     --playlist-random               Download playlist videos in random order
     --xattr-set-filesize            Set file xattribute ytdl.filesize with
                                     expected file size
@@ -2000,6 +1996,10 @@ #### Redundant options
     --max-views COUNT                --match-filter "view_count <=? COUNT"
     --user-agent UA                  --add-header "User-Agent:UA"
     --referer URL                    --add-header "Referer:URL"
+    --playlist-start NUMBER          -I NUMBER:
+    --playlist-end NUMBER            -I :NUMBER
+    --playlist-reverse               -I ::-1
+    --no-playlist-reverse            Default
 
 
 #### Not recommended

test/test_YoutubeDL.py

@@ -23,6 +23,7 @@
 from yt_dlp.utils import (
     ExtractorError,
     LazyList,
+    OnDemandPagedList,
     int_or_none,
     match_filter_func,
 )
@@ -989,41 +990,79 @@ def f(v, incomplete):
         self.assertEqual(res, [])
 
     def test_playlist_items_selection(self):
-        entries = [{
-            'id': compat_str(i),
-            'title': compat_str(i),
-            'url': TEST_URL,
-        } for i in range(1, 5)]
-        playlist = {
-            '_type': 'playlist',
-            'id': 'test',
-            'entries': entries,
-            'extractor': 'test:playlist',
-            'extractor_key': 'test:playlist',
-            'webpage_url': 'http://example.com',
-        }
+        INDICES, PAGE_SIZE = list(range(1, 11)), 3
 
-        def get_downloaded_info_dicts(params):
+        def entry(i, evaluated):
+            evaluated.append(i)
+            return {
+                'id': str(i),
+                'title': str(i),
+                'url': TEST_URL,
+            }
+
+        def pagedlist_entries(evaluated):
+            def page_func(n):
+                start = PAGE_SIZE * n
+                for i in INDICES[start: start + PAGE_SIZE]:
+                    yield entry(i, evaluated)
+            return OnDemandPagedList(page_func, PAGE_SIZE)
+
+        def page_num(i):
+            return (i + PAGE_SIZE - 1) // PAGE_SIZE
+
+        def generator_entries(evaluated):
+            for i in INDICES:
+                yield entry(i, evaluated)
+
+        def list_entries(evaluated):
+            return list(generator_entries(evaluated))
+
+        def lazylist_entries(evaluated):
+            return LazyList(generator_entries(evaluated))
+
+        def get_downloaded_info_dicts(params, entries):
             ydl = YDL(params)
-            # make a deep copy because the dictionary and nested entries
-            # can be modified
-            ydl.process_ie_result(copy.deepcopy(playlist))
+            ydl.process_ie_result({
+                '_type': 'playlist',
+                'id': 'test',
+                'extractor': 'test:playlist',
+                'extractor_key': 'test:playlist',
+                'webpage_url': 'http://example.com',
+                'entries': entries,
+            })
             return ydl.downloaded_info_dicts
 
-        def test_selection(params, expected_ids):
-            results = [
-                (v['playlist_autonumber'] - 1, (int(v['id']), v['playlist_index']))
-                for v in get_downloaded_info_dicts(params)]
-            self.assertEqual(results, list(enumerate(zip(expected_ids, expected_ids))))
+        def test_selection(params, expected_ids, evaluate_all=False):
+            expected_ids = list(expected_ids)
+            if evaluate_all:
+                generator_eval = pagedlist_eval = INDICES
+            elif not expected_ids:
+                generator_eval = pagedlist_eval = []
+            else:
+                generator_eval = INDICES[0: max(expected_ids)]
+                pagedlist_eval = INDICES[PAGE_SIZE * page_num(min(expected_ids)) - PAGE_SIZE:
+                                         PAGE_SIZE * page_num(max(expected_ids))]
 
-        test_selection({}, [1, 2, 3, 4])
-        test_selection({'playlistend': 10}, [1, 2, 3, 4])
-        test_selection({'playlistend': 2}, [1, 2])
-        test_selection({'playliststart': 10}, [])
-        test_selection({'playliststart': 2}, [2, 3, 4])
-        test_selection({'playlist_items': '2-4'}, [2, 3, 4])
+            for name, func, expected_eval in (
+                ('list', list_entries, INDICES),
+                ('Generator', generator_entries, generator_eval),
+                ('LazyList', lazylist_entries, generator_eval),
+                ('PagedList', pagedlist_entries, pagedlist_eval),
+            ):
+                evaluated = []
+                entries = func(evaluated)
+                results = [(v['playlist_autonumber'] - 1, (int(v['id']), v['playlist_index']))
+                           for v in get_downloaded_info_dicts(params, entries)]
+                self.assertEqual(results, list(enumerate(zip(expected_ids, expected_ids))), f'Entries of {name} for {params}')
+                self.assertEqual(sorted(evaluated), expected_eval, f'Evaluation of {name} for {params}')
+        test_selection({}, INDICES)
+        test_selection({'playlistend': 20}, INDICES, True)
+        test_selection({'playlistend': 2}, INDICES[:2])
+        test_selection({'playliststart': 11}, [], True)
+        test_selection({'playliststart': 2}, INDICES[1:])
+        test_selection({'playlist_items': '2-4'}, INDICES[1:4])
         test_selection({'playlist_items': '2,4'}, [2, 4])
-        test_selection({'playlist_items': '10'}, [])
+        test_selection({'playlist_items': '20'}, [], True)
         test_selection({'playlist_items': '0'}, [])
 
         # Tests for https://github.com/ytdl-org/youtube-dl/issues/10591
@@ -1032,11 +1071,33 @@ def test_selection(params, expected_ids):
 
         # Tests for https://github.com/yt-dlp/yt-dlp/issues/720
         # https://github.com/yt-dlp/yt-dlp/issues/302
-        test_selection({'playlistreverse': True}, [4, 3, 2, 1])
-        test_selection({'playliststart': 2, 'playlistreverse': True}, [4, 3, 2])
+        test_selection({'playlistreverse': True}, INDICES[::-1])
+        test_selection({'playliststart': 2, 'playlistreverse': True}, INDICES[:0:-1])
         test_selection({'playlist_items': '2,4', 'playlistreverse': True}, [4, 2])
         test_selection({'playlist_items': '4,2'}, [4, 2])
 
+        # Tests for --playlist-items start:end:step
+        test_selection({'playlist_items': ':'}, INDICES, True)
+        test_selection({'playlist_items': '::1'}, INDICES, True)
+        test_selection({'playlist_items': '::-1'}, INDICES[::-1], True)
+        test_selection({'playlist_items': ':6'}, INDICES[:6])
+        test_selection({'playlist_items': ':-6'}, INDICES[:-5], True)
+        test_selection({'playlist_items': '-1:6:-2'}, INDICES[:4:-2], True)
+        test_selection({'playlist_items': '9:-6:-2'}, INDICES[8:3:-2], True)
+
+        test_selection({'playlist_items': '1:inf:2'}, INDICES[::2], True)
+        test_selection({'playlist_items': '-2:inf'}, INDICES[-2:], True)
+        test_selection({'playlist_items': ':inf:-1'}, [], True)
+        test_selection({'playlist_items': '0-2:2'}, [2])
+        test_selection({'playlist_items': '1-:2'}, INDICES[::2], True)
+        test_selection({'playlist_items': '0--2:2'}, INDICES[1:-1:2], True)
+
+        test_selection({'playlist_items': '10::3'}, [10], True)
+        test_selection({'playlist_items': '-1::3'}, [10], True)
+        test_selection({'playlist_items': '11::3'}, [], True)
+        test_selection({'playlist_items': '-15::2'}, INDICES[1::2], True)
+        test_selection({'playlist_items': '-15::15'}, [], True)
+
     def test_urlopen_no_file_protocol(self):
         # see https://github.com/ytdl-org/youtube-dl/issues/8227
         ydl = YDL()

yt_dlp/YoutubeDL.py

@@ -74,13 +74,13 @@
     ExtractorError,
     GeoRestrictedError,
     HEADRequest,
-    InAdvancePagedList,
     ISO3166Utils,
     LazyList,
     MaxDownloadsReached,
     Namespace,
     PagedList,
     PerRequestProxyHandler,
+    PlaylistEntries,
     Popen,
     PostProcessingError,
     ReExtractInfo,
@@ -1410,7 +1410,7 @@ def extract_info(self, url, download=True, ie_key=None, extra_info=None,
         else:
             self.report_error('no suitable InfoExtractor for URL %s' % url)
 
-    def __handle_extraction_exceptions(func):
+    def _handle_extraction_exceptions(func):
         @functools.wraps(func)
         def wrapper(self, *args, **kwargs):
             while True:
@@ -1483,7 +1483,7 @@ def progress(msg):
                 self.to_screen('')
             raise
 
-    @__handle_extraction_exceptions
+    @_handle_extraction_exceptions
     def __extract_info(self, url, ie, download, extra_info, process):
         ie_result = ie.extract(url)
         if ie_result is None:  # Finished already (backwards compatibility; listformats and friends should be moved here)
@@ -1666,105 +1666,14 @@ def _playlist_infodict(ie_result, **kwargs):
         }
 
     def __process_playlist(self, ie_result, download):
-        # We process each entry in the playlist
-        playlist = ie_result.get('title') or ie_result.get('id')
-        self.to_screen('[download] Downloading playlist: %s' % playlist)
+        """Process each entry in the playlist"""
+        title = ie_result.get('title') or ie_result.get('id') or '<Untitled>'
+        self.to_screen(f'[download] Downloading playlist: {title}')
 
-        if 'entries' not in ie_result:
-            raise EntryNotInPlaylist('There are no entries')
-
-        MissingEntry = object()
-        incomplete_entries = bool(ie_result.get('requested_entries'))
-        if incomplete_entries:
-            def fill_missing_entries(entries, indices):
-                ret = [MissingEntry] * max(indices)
-                for i, entry in zip(indices, entries):
-                    ret[i - 1] = entry
-                return ret
-            ie_result['entries'] = fill_missing_entries(ie_result['entries'], ie_result['requested_entries'])
-
-        playlist_results = []
-
-        playliststart = self.params.get('playliststart', 1)
-        playlistend = self.params.get('playlistend')
-        # For backwards compatibility, interpret -1 as whole list
-        if playlistend == -1:
-            playlistend = None
-
-        playlistitems_str = self.params.get('playlist_items')
-        playlistitems = None
-        if playlistitems_str is not None:
-            def iter_playlistitems(format):
-                for string_segment in format.split(','):
-                    if '-' in string_segment:
-                        start, end = string_segment.split('-')
-                        for item in range(int(start), int(end) + 1):
-                            yield int(item)
-                    else:
-                        yield int(string_segment)
-            playlistitems = orderedSet(iter_playlistitems(playlistitems_str))
-
-        ie_entries = ie_result['entries']
-        if isinstance(ie_entries, list):
-            playlist_count = len(ie_entries)
-            msg = f'Collected {playlist_count} videos; downloading %d of them'
-            ie_result['playlist_count'] = ie_result.get('playlist_count') or playlist_count
-
-            def get_entry(i):
-                return ie_entries[i - 1]
-        else:
-            msg = 'Downloading %d videos'
-            if not isinstance(ie_entries, (PagedList, LazyList)):
-                ie_entries = LazyList(ie_entries)
-            elif isinstance(ie_entries, InAdvancePagedList):
-                if ie_entries._pagesize == 1:
-                    playlist_count = ie_entries._pagecount
-
-            def get_entry(i):
-                return YoutubeDL.__handle_extraction_exceptions(
-                    lambda self, i: ie_entries[i - 1]
-                )(self, i)
-
-        entries, broken = [], False
-        items = playlistitems if playlistitems is not None else itertools.count(playliststart)
-        for i in items:
-            if i == 0:
-                continue
-            if playlistitems is None and playlistend is not None and playlistend < i:
-                break
-            entry = None
-            try:
-                entry = get_entry(i)
-                if entry is MissingEntry:
-                    raise EntryNotInPlaylist()
-            except (IndexError, EntryNotInPlaylist):
-                if incomplete_entries:
-                    raise EntryNotInPlaylist(f'Entry {i} cannot be found')
-                elif not playlistitems:
-                    break
-            entries.append(entry)
-            try:
-                if entry is not None:
-                    # TODO: Add auto-generated fields
-                    self._match_entry(entry, incomplete=True, silent=True)
-            except (ExistingVideoReached, RejectedVideoReached):
-                broken = True
-                break
-        ie_result['entries'] = entries
-
-        # Save playlist_index before re-ordering
-        entries = [
-            ((playlistitems[i - 1] if playlistitems else i + playliststart - 1), entry)
-            for i, entry in enumerate(entries, 1)
-            if entry is not None]
-        n_entries = len(entries)
-
-        if not (ie_result.get('playlist_count') or broken or playlistitems or playlistend):
-            ie_result['playlist_count'] = n_entries
-
-        if not playlistitems and (playliststart != 1 or playlistend):
-            playlistitems = list(range(playliststart, playliststart + n_entries))
-        ie_result['requested_entries'] = playlistitems
+        all_entries = PlaylistEntries(self, ie_result)
+        entries = orderedSet(all_entries.get_requested_items())
+        ie_result['requested_entries'], ie_result['entries'] = tuple(zip(*entries)) or ([], [])
+        n_entries, ie_result['playlist_count'] = len(entries), all_entries.full_count
 
         _infojson_written = False
         write_playlist_files = self.params.get('allow_playlist_files', True)
@@ -1787,28 +1696,29 @@ def get_entry(i):
         if self.params.get('playlistrandom', False):
             random.shuffle(entries)
 
-        x_forwarded_for = ie_result.get('__x_forwarded_for_ip')
+        self.to_screen(f'[{ie_result["extractor"]}] Playlist {title}: Downloading {n_entries} videos'
+                       f'{format_field(ie_result, "playlist_count", " of %s")}')
 
-        self.to_screen(f'[{ie_result["extractor"]}] playlist {playlist}: {msg % n_entries}')
         failures = 0
         max_failures = self.params.get('skip_playlist_after_errors') or float('inf')
-        for i, entry_tuple in enumerate(entries, 1):
-            playlist_index, entry = entry_tuple
-            if 'playlist-index' in self.params['compat_opts']:
-                playlist_index = playlistitems[i - 1] if playlistitems else i + playliststart - 1
+        for i, (playlist_index, entry) in enumerate(entries, 1):
+            # TODO: Add auto-generated fields
+            if self._match_entry(entry, incomplete=True) is not None:
+                continue
+
+            if 'playlist-index' in self.params.get('compat_opts', []):
+                playlist_index = ie_result['requested_entries'][i - 1]
             self.to_screen('[download] Downloading video %s of %s' % (
                 self._format_screen(i, self.Styles.ID), self._format_screen(n_entries, self.Styles.EMPHASIS)))
-            # This __x_forwarded_for_ip thing is a bit ugly but requires
-            # minimal changes
-            if x_forwarded_for:
-                entry['__x_forwarded_for_ip'] = x_forwarded_for
-            extra = {
+
+            entry['__x_forwarded_for_ip'] = ie_result.get('__x_forwarded_for_ip')
+            entry_result = self.__process_iterable_entry(entry, download, {
                 'n_entries': n_entries,
-                '__last_playlist_index': max(playlistitems) if playlistitems else (playlistend or n_entries),
+                '__last_playlist_index': max(ie_result['requested_entries']),
                 'playlist_count': ie_result.get('playlist_count'),
                 'playlist_index': playlist_index,
                 'playlist_autonumber': i,
-                'playlist': playlist,
+                'playlist': title,
                 'playlist_id': ie_result.get('id'),
                 'playlist_title': ie_result.get('title'),
                 'playlist_uploader': ie_result.get('uploader'),
@@ -1818,20 +1728,17 @@ def get_entry(i):
                 'webpage_url_basename': url_basename(ie_result['webpage_url']),
                 'webpage_url_domain': get_domain(ie_result['webpage_url']),
                 'extractor_key': ie_result['extractor_key'],
-            }
-
-            if self._match_entry(entry, incomplete=True) is not None:
-                continue
-
-            entry_result = self.__process_iterable_entry(entry, download, extra)
+            })
             if not entry_result:
                 failures += 1
             if failures >= max_failures:
                 self.report_error(
-                    'Skipping the remaining entries in playlist "%s" since %d items failed extraction' % (playlist, failures))
+                    f'Skipping the remaining entries in playlist "{title}" since {failures} items failed extraction')
                 break
-            playlist_results.append(entry_result)
-        ie_result['entries'] = playlist_results
+            entries[i - 1] = (playlist_index, entry_result)
+
+        # Update with processed data
+        ie_result['requested_entries'], ie_result['entries'] = tuple(zip(*entries)) or ([], [])
 
         # Write the updated info to json
         if _infojson_written is True and self._write_info_json(
@@ -1840,10 +1747,10 @@ def get_entry(i):
             return
 
         ie_result = self.run_all_pps('playlist', ie_result)
-        self.to_screen(f'[download] Finished downloading playlist: {playlist}')
+        self.to_screen(f'[download] Finished downloading playlist: {title}')
         return ie_result
 
-    @__handle_extraction_exceptions
+    @_handle_extraction_exceptions
     def __process_iterable_entry(self, entry, download, extra_info):
         return self.process_ie_result(
             entry, download=download, extra_info=extra_info)

yt_dlp/__init__.py

@@ -33,6 +33,7 @@
     DownloadCancelled,
     DownloadError,
     GeoUtils,
+    PlaylistEntries,
     SameFileError,
     decodeOption,
     download_range_func,
@@ -372,6 +373,12 @@ def metadataparser_actions(f):
     opts.parse_metadata = list(itertools.chain(*map(metadataparser_actions, parse_metadata)))
 
     # Other options
+    if opts.playlist_items is not None:
+        try:
+            tuple(PlaylistEntries.parse_playlist_items(opts.playlist_items))
+        except Exception as err:
+            raise ValueError(f'Invalid playlist-items {opts.playlist_items!r}: {err}')
+
     geo_bypass_code = opts.geo_bypass_ip_block or opts.geo_bypass_country
     if geo_bypass_code is not None:
         try:

yt_dlp/options.py

@@ -500,15 +500,19 @@ def _alias_callback(option, opt_str, value, parser, opts, nargs):
     selection.add_option(
         '--playlist-start',
         dest='playliststart', metavar='NUMBER', default=1, type=int,
-        help='Playlist video to start at (default is %default)')
+        help=optparse.SUPPRESS_HELP)
     selection.add_option(
         '--playlist-end',
         dest='playlistend', metavar='NUMBER', default=None, type=int,
-        help='Playlist video to end at (default is last)')
+        help=optparse.SUPPRESS_HELP)
     selection.add_option(
-        '--playlist-items',
+        '-I', '--playlist-items',
         dest='playlist_items', metavar='ITEM_SPEC', default=None,
-        help='Playlist video items to download. Specify indices of the videos in the playlist separated by commas like: "--playlist-items 1,2,5,8" if you want to download videos indexed 1, 2, 5, 8 in the playlist. You can specify range: "--playlist-items 1-3,7,10-13", it will download the videos at index 1, 2, 3, 7, 10, 11, 12 and 13')
+        help=(
+            'Comma seperated playlist_index of the videos to download. '
+            'You can specify a range using "[START]:[STOP][:STEP]". For backward compatibility, START-STOP is also supported. '
+            'Use negative indices to count from the right and negative STEP to download in reverse order. '
+            'Eg: "-I 1:3,7,-5::2" used on a playlist of size 15 will download the videos at index 1,2,3,7,11,13,15'))
     selection.add_option(
         '--match-title',
         dest='matchtitle', metavar='REGEX',
@@ -885,11 +889,11 @@ def _alias_callback(option, opt_str, value, parser, opts, nargs):
     downloader.add_option(
         '--playlist-reverse',
         action='store_true',
-        help='Download playlist videos in reverse order')
+        help=optparse.SUPPRESS_HELP)
     downloader.add_option(
         '--no-playlist-reverse',
         action='store_false', dest='playlist_reverse',
-        help='Download playlist videos in default order (default)')
+        help=optparse.SUPPRESS_HELP)
     downloader.add_option(
         '--playlist-random',
         action='store_true',

yt_dlp/utils.py

@@ -2609,6 +2609,16 @@ def get_exe_version(exe, args=['--version'],
     return detect_exe_version(out, version_re, unrecognized) if out else False
 
 
+def frange(start=0, stop=None, step=1):
+    """Float range"""
+    if stop is None:
+        start, stop = 0, start
+    sign = [-1, 1][step > 0] if step else 0
+    while sign * start < sign * stop:
+        yield start
+        start += step
+
+
 class LazyList(collections.abc.Sequence):
     """Lazy immutable list from an iterable
     Note that slices of a LazyList are lists and not LazyList"""
@@ -2805,6 +2815,148 @@ def _getslice(self, start, end):
             yield from page_results
 
 
+class PlaylistEntries:
+    MissingEntry = object()
+    is_exhausted = False
+
+    def __init__(self, ydl, info_dict):
+        self.ydl, self.info_dict = ydl, info_dict
+
+    PLAYLIST_ITEMS_RE = re.compile(r'''(?x)
+        (?P<start>[+-]?\d+)?
+        (?P<range>[:-]
+            (?P<end>[+-]?\d+|inf(?:inite)?)?
+            (?::(?P<step>[+-]?\d+))?
+        )?''')
+
+    @classmethod
+    def parse_playlist_items(cls, string):
+        for segment in string.split(','):
+            if not segment:
+                raise ValueError('There is two or more consecutive commas')
+            mobj = cls.PLAYLIST_ITEMS_RE.fullmatch(segment)
+            if not mobj:
+                raise ValueError(f'{segment!r} is not a valid specification')
+            start, end, step, has_range = mobj.group('start', 'end', 'step', 'range')
+            if int_or_none(step) == 0:
+                raise ValueError(f'Step in {segment!r} cannot be zero')
+            yield slice(int_or_none(start), float_or_none(end), int_or_none(step)) if has_range else int(start)
+
+    def get_requested_items(self):
+        playlist_items = self.ydl.params.get('playlist_items')
+        playlist_start = self.ydl.params.get('playliststart', 1)
+        playlist_end = self.ydl.params.get('playlistend')
+        # For backwards compatibility, interpret -1 as whole list
+        if playlist_end in (-1, None):
+            playlist_end = ''
+        if not playlist_items:
+            playlist_items = f'{playlist_start}:{playlist_end}'
+        elif playlist_start != 1 or playlist_end:
+            self.ydl.report_warning('Ignoring playliststart and playlistend because playlistitems was given', only_once=True)
+
+        for index in self.parse_playlist_items(playlist_items):
+            for i, entry in self[index]:
+                yield i, entry
+                try:
+                    # TODO: Add auto-generated fields
+                    self.ydl._match_entry(entry, incomplete=True, silent=True)
+                except (ExistingVideoReached, RejectedVideoReached):
+                    return
+
+    @property
+    def full_count(self):
+        if self.info_dict.get('playlist_count'):
+            return self.info_dict['playlist_count']
+        elif self.is_exhausted and not self.is_incomplete:
+            return len(self)
+        elif isinstance(self._entries, InAdvancePagedList):
+            if self._entries._pagesize == 1:
+                return self._entries._pagecount
+
+    @functools.cached_property
+    def _entries(self):
+        entries = self.info_dict.get('entries')
+        if entries is None:
+            raise EntryNotInPlaylist('There are no entries')
+        elif isinstance(entries, list):
+            self.is_exhausted = True
+
+        indices = self.info_dict.get('requested_entries')
+        self.is_incomplete = bool(indices)
+        if self.is_incomplete:
+            assert self.is_exhausted
+            ret = [self.MissingEntry] * max(indices)
+            for i, entry in zip(indices, entries):
+                ret[i - 1] = entry
+            return ret
+
+        if isinstance(entries, (list, PagedList, LazyList)):
+            return entries
+        return LazyList(entries)
+
+    @functools.cached_property
+    def _getter(self):
+        if isinstance(self._entries, list):
+            def get_entry(i):
+                try:
+                    entry = self._entries[i]
+                except IndexError:
+                    entry = self.MissingEntry
+                    if not self.is_incomplete:
+                        raise self.IndexError()
+                if entry is self.MissingEntry:
+                    raise EntryNotInPlaylist(f'Entry {i} cannot be found')
+                return entry
+        else:
+            def get_entry(i):
+                try:
+                    return type(self.ydl)._handle_extraction_exceptions(lambda _, i: self._entries[i])(self.ydl, i)
+                except (LazyList.IndexError, PagedList.IndexError):
+                    raise self.IndexError()
+        return get_entry
+
+    def __getitem__(self, idx):
+        if isinstance(idx, int):
+            idx = slice(idx, idx)
+
+        # NB: PlaylistEntries[1:10] => (0, 1, ... 9)
+        step = 1 if idx.step is None else idx.step
+        if idx.start is None:
+            start = 0 if step > 0 else len(self) - 1
+        else:
+            start = idx.start - 1 if idx.start >= 0 else len(self) + idx.start
+
+        # NB: Do not call len(self) when idx == [:]
+        if idx.stop is None:
+            stop = 0 if step < 0 else float('inf')
+        else:
+            stop = idx.stop - 1 if idx.stop >= 0 else len(self) + idx.stop
+        stop += [-1, 1][step > 0]
+
+        for i in frange(start, stop, step):
+            if i < 0:
+                continue
+            try:
+                try:
+                    entry = self._getter(i)
+                except self.IndexError:
+                    self.is_exhausted = True
+                    if step > 0:
+                        break
+                    continue
+            except IndexError:
+                if self.is_exhausted:
+                    break
+                raise
+            yield i + 1, entry
+
+    def __len__(self):
+        return len(tuple(self[:]))
+
+    class IndexError(IndexError):
+        pass
+
+
 def uppercase_escape(s):
     unicode_escape = codecs.getdecoder('unicode_escape')
     return re.sub(