[utils] Add dict_get convenience method

test/test_utils.py

@@ -22,6 +22,7 @@ from youtube_dl.utils import (
     DateRange,
     detect_exe_version,
     determine_ext,
+    dict_get,
     encode_compat_str,
     encodeFilename,
     escape_rfc3986,
@@ -450,6 +451,19 @@ class TestUtil(unittest.TestCase):
         data = urlencode_postdata({'username': 'foo@bar.com', 'password': '1234'})
         self.assertTrue(isinstance(data, bytes))
 
+    def test_dict_get(self):
+        d = {
+            'a': 42,
+        }
+        self.assertEqual(dict_get(d, 'a'), 42)
+        self.assertEqual(dict_get(d, 'b'), None)
+        self.assertEqual(dict_get(d, 'b', 42), 42)
+        self.assertEqual(dict_get(d, ('a', )), 42)
+        self.assertEqual(dict_get(d, ('b', 'a', )), 42)
+        self.assertEqual(dict_get(d, ('b', 'c', 'a', 'd', )), 42)
+        self.assertEqual(dict_get(d, ('b', 'c', )), None)
+        self.assertEqual(dict_get(d, ('b', 'c', ), 42), 42)
+
     def test_encode_compat_str(self):
         self.assertEqual(encode_compat_str(b'\xd1\x82\xd0\xb5\xd1\x81\xd1\x82', 'utf-8'), 'тест')
         self.assertEqual(encode_compat_str('тест', 'utf-8'), 'тест')

youtube_dl/utils.py

@@ -1717,6 +1717,15 @@ def encode_dict(d, encoding='utf-8'):
     return dict((encode(k), encode(v)) for k, v in d.items())
 
 
+def dict_get(d, key_or_keys, default=None):
+    if isinstance(key_or_keys, (list, tuple)):
+        for key in key_or_keys:
+            if d.get(key):
+                return d[key]
+        return default
+    return d.get(key_or_keys, default)
+
+
 def encode_compat_str(string, encoding=preferredencoding(), errors='strict'):
     return string if isinstance(string, compat_str) else compat_str(string, encoding, errors)