[utils] Generalize `traverse_dict` to `traverse_obj`

3 files changed, 34 insertions, 17 deletions

diff --git a/yt_dlp/YoutubeDL.py b/yt_dlp/YoutubeDL.py
index 2997b19ca..1643649fb 100644
--- a/yt_dlp/YoutubeDL.py
+++ b/yt_dlp/YoutubeDL.py
@@ -101,7 +101,7 @@ from .utils import (
     strftime_or_none,
     subtitles_filename,
     to_high_limit_path,
-    traverse_dict,
+    traverse_obj,
     UnavailableVideoError,
     url_basename,
     version_tuple,
@@ -855,7 +855,7 @@ class YoutubeDL(object):
         def get_value(mdict):
             # Object traversal
             fields = mdict['fields'].split('.')
-            value = traverse_dict(info_dict, fields)
+            value = traverse_obj(info_dict, fields)
             # Negative
             if mdict['negate']:
                 value = float_or_none(value)
@@ -872,7 +872,7 @@ class YoutubeDL(object):
                         item, multiplier = (item[1:], -1) if item[0] == '-' else (item, 1)
                         offset = float_or_none(item)
                         if offset is None:
-                            offset = float_or_none(traverse_dict(info_dict, item.split('.')))
+                            offset = float_or_none(traverse_obj(info_dict, item.split('.')))
                         try:
                             value = operator(value, multiplier * offset)
                         except (TypeError, ZeroDivisionError):
diff --git a/yt_dlp/postprocessor/ffmpeg.py b/yt_dlp/postprocessor/ffmpeg.py
index d9f816b04..374da8c02 100644
--- a/yt_dlp/postprocessor/ffmpeg.py
+++ b/yt_dlp/postprocessor/ffmpeg.py
@@ -23,7 +23,7 @@ from ..utils import (
     ISO639Utils,
     process_communicate_or_kill,
     replace_extension,
-    traverse_dict,
+    traverse_obj,
 )
 
 
@@ -229,7 +229,7 @@ class FFmpegPostProcessor(PostProcessor):
     def get_stream_number(self, path, keys, value):
         streams = self.get_metadata_object(path)['streams']
         num = next(
-            (i for i, stream in enumerate(streams) if traverse_dict(stream, keys, casesense=False) == value),
+            (i for i, stream in enumerate(streams) if traverse_obj(stream, keys, casesense=False) == value),
             None)
         return num, len(streams)
 
diff --git a/yt_dlp/utils.py b/yt_dlp/utils.py
index 72fd8a0e7..6737c1965 100644
--- a/yt_dlp/utils.py
+++ b/yt_dlp/utils.py
@@ -6181,21 +6181,38 @@ def load_plugins(name, suffix, namespace):
     return classes
 
 
-def traverse_dict(dictn, keys, casesense=True):
+def traverse_obj(obj, keys, *, casesense=True, is_user_input=False, traverse_string=False):
+    ''' Traverse nested list/dict/tuple
+    @param casesense        Whether to consider dictionary keys as case sensitive
+    @param is_user_input    Whether the keys are generated from user input. If True,
+                            strings are converted to int/slice if necessary
+    @param traverse_string  Whether to traverse inside strings. If True, any
+                            non-compatible object will also be converted into a string
+    '''
     keys = list(keys)[::-1]
     while keys:
         key = keys.pop()
-        if isinstance(dictn, dict):
+        if isinstance(obj, dict):
+            assert isinstance(key, compat_str)
             if not casesense:
-                dictn = {k.lower(): v for k, v in dictn.items()}
+                obj = {k.lower(): v for k, v in obj.items()}
                 key = key.lower()
-            dictn = dictn.get(key)
-        elif isinstance(dictn, (list, tuple, compat_str)):
-            if ':' in key:
-                key = slice(*map(int_or_none, key.split(':')))
-            else:
-                key = int_or_none(key)
-            dictn = try_get(dictn, lambda x: x[key])
+            obj = obj.get(key)
         else:
-            return None
-    return dictn
+            if is_user_input:
+                key = (int_or_none(key) if ':' not in key
+                       else slice(*map(int_or_none, key.split(':'))))
+            if not isinstance(obj, (list, tuple)):
+                if traverse_string:
+                    obj = compat_str(obj)
+                else:
+                    return None
+            assert isinstance(key, (int, slice))
+            obj = try_get(obj, lambda x: x[key])
+    return obj
+
+
+def traverse_dict(dictn, keys, casesense=True):
+    ''' For backward compatibility. Do not use '''
+    return traverse_obj(dictn, keys, casesense=casesense,
+                        is_user_input=True, traverse_string=True)