added likely_metadata

--HG--
extra : convert_revision : svn%3A41726ec3-264d-0410-9c23-a9f1637257cc/trunk%40196

beets/autotag/__init__.py

@@ -0,0 +1,45 @@
+from collections import defaultdict
+from beets.autotag.mb import match_album
+
+def likely_metadata(items):
+    """Returns the most likely artist and album for a set of Items.
+    Each is determined by tag reflected by the plurality of the Items.
+    """
+
+    # The tags we'll try to determine.
+    keys = 'artist', 'album'
+
+    # Make dictionaries in which to count the freqencies of different
+    # artist and album tags. We'll use this to find the most likely
+    # artist and album. Defaultdicts let the frequency default to zero.
+    freqs = {}
+    for key in keys:
+        freqs[key] = defaultdict(int)
+
+    # Count the frequencies.
+    for item in items:
+        for key in keys:
+            value = getattr(item, key)
+            if value: # Don't count empty tags.
+                freqs[key][value] += 1
+
+    # Find max-frequency tags.
+    likelies = {}
+    for key in keys:
+        max_freq = 0
+        likelies[key] = None
+        for tag, freq in freqs[key].items():
+            if freq > max_freq:
+                max_freq = freq
+                likelies[key] = tag
+    
+    return (likelies['artist'], likelies['album'])
+
+if __name__ == '__main__': # Smoke test.
+    from beets.library import Item
+    items = [Item({'artist': 'The Beatles', 'album': 'The White Album'}),
+             Item({'artist': 'The Beetles', 'album': 'The White Album'}),
+             Item({'artist': 'The Beatles', 'album': 'Teh White Album'})]
+    print likely_metadata(items)
+
+

test/test_autotag.py

@@ -6,7 +6,18 @@ import sys
 import time
 import musicbrainz2.model
 sys.path.append('..')
+from beets import autotag
 from beets.autotag import mb
+from beets.library import Item
+
+class AutotagTest(unittest.TestCase):
+    def test_likely_metadata_finds_pluralities(self):
+        items = [Item({'artist': 'The Beetles', 'album': 'The White Album'}),
+                 Item({'artist': 'The Beatles', 'album': 'The White Album'}),
+                 Item({'artist': 'The Beatles', 'album': 'Teh White Album'})]
+        l_artist, l_album = autotag.likely_metadata(items)
+        self.assertEqual(l_artist, 'The Beatles')
+        self.assertEqual(l_album, 'The White Album')
 
 class MBQueryWaitTest(unittest.TestCase):
     def setup(self):