Switched fingerprint_directory to using multiprocessing.Pool

Fixed an issue of 'grouper' items being generators due to ifilter usage.
Temporary fix applied for the need of referencing SQLDatabase.FIELD_SONGNAME in __init__
Cleaned up some pep8 style issues

dejavu/__init__.py

@@ -1,9 +1,8 @@
 from dejavu.database import get_database
 import dejavu.decoder as decoder
 import fingerprint
-from multiprocessing import Process, cpu_count
+import multiprocessing
 import os
-import random
 
 
 class Dejavu(object):
@@ -30,57 +29,39 @@ class Dejavu(object):
 
     def fingerprint_directory(self, path, extensions, nprocesses=None):
         # Try to use the maximum amount of processes if not given.
-        if nprocesses is None:
-            try:
-                nprocesses = cpu_count()
-            except NotImplementedError:
-                nprocesses = 1
+        try:
+            nprocesses = nprocesses or multiprocessing.cpu_count()
+        except NotImplementedError:
+            nprocesses = 1
+        else:
+            nprocesses = 1 if nprocesses <= 0 else nprocesses
 
-        # convert files, shuffle order
-        files = list(decoder.find_files(path, extensions))
-        random.shuffle(files)
+        pool = multiprocessing.Pool(nprocesses)
 
-        files_split = chunkify(files, nprocesses)
+        results = []
+        for filename, _ in decoder.find_files(path, extensions):
+            # TODO: Don't queue up files that have already been fingerprinted.
+            result = pool.apply_async(_fingerprint_worker,
+                                      (filename, self.db))
+            results.append(result)
 
-        # split into processes here
-        processes = []
-        for i in range(nprocesses):
+        while len(results):
+            for result in results[:]:
+                # TODO: Handle errors gracefully and return them to the callee
+                # in some way.
+                try:
+                    result.get(timeout=2)
+                except multiprocessing.TimeoutError:
+                    continue
+                except:
+                    import traceback, sys
+                    traceback.print_exc(file=sys.stdout)
+                    results.remove(result)
+                else:
+                    results.remove(result)
 
-            # create process and start it
-            p = Process(target=self._fingerprint_worker,
-                        args=(files_split[i], self.db))
-            p.start()
-            processes.append(p)
-
-        # wait for all processes to complete
-        for p in processes:
-            p.join()
-
-    def _fingerprint_worker(self, files, db):
-        for filename, extension in files:
-
-            # if there are already fingerprints in database,
-            # don't re-fingerprint
-            song_name = os.path.basename(filename).split(".")[0]
-            if song_name in self.songnames_set:
-                print("-> Already fingerprinted, continuing...")
-                continue
-
-            channels, Fs = decoder.read(filename)
-
-            # insert song name into database
-            song_id = db.insert_song(song_name)
-
-            for c in range(len(channels)):
-                channel = channels[c]
-                print "-> Fingerprinting channel %d of song %s..." % (c+1, song_name)
-
-                hashes = fingerprint.fingerprint(channel, Fs=Fs)
-
-                db.insert_hashes(song_id, hashes)
-
-            # only after done fingerprinting do confirm
-            db.set_song_fingerprinted(song_id)
+        pool.close()
+        pool.join()
 
     def fingerprint_file(self, filepath, song_name=None):
         channels, Fs = decoder.read(filepath)
@@ -122,12 +103,14 @@ class Dejavu(object):
                 largest_count = diff_counter[diff][sid]
                 song_id = sid
 
-        print("Diff is %d with %d offset-aligned matches" % (largest, largest_count))
+        print("Diff is %d with %d offset-aligned matches" % (largest,
+                                                             largest_count))
 
         # extract idenfication
         song = self.db.get_song_by_id(song_id)
         if song:
-            songname = song.get(SQLDatabase.FIELD_SONGNAME, None)
+            # TODO: Clarifey what `get_song_by_id` should return.
+            songname = song.get("song_name", None)
         else:
             return None
 
@@ -145,6 +128,35 @@ class Dejavu(object):
         return r.recognize(*options, **kwoptions)
 
 
+def _fingerprint_worker(filename, db):
+    song_name, extension = os.path.splitext(os.path.basename(filename))
+
+    channels, Fs = decoder.read(filename)
+
+    # insert song into database
+    sid = db.insert_song(song_name)
+
+    channel_amount = len(channels)
+    for channeln, channel in enumerate(channels):
+        # TODO: Remove prints or change them into optional logging.
+        print("Fingerprinting channel %d/%d for %s" % (channeln + 1,
+                                                       channel_amount,
+                                                       filename))
+        hashes = fingerprint.fingerprint(channel, Fs=Fs)
+        print("Finished channel %d/%d for %s" % (channeln + 1, channel_amount,
+                                                 filename))
+
+        print("Inserting fingerprints for channel %d/%d for %s" %
+              (channeln + 1, channel_amount, filename))
+        db.insert_hashes(sid, hashes)
+        print("Finished inserting for channel %d/%d for  %s" %
+              (channeln + 1, channel_amount, filename))
+
+    print("Marking %s finished" % (filename,))
+    db.set_song_fingerprinted(sid)
+    print("%s finished" % (filename,))
+
+
 def chunkify(lst, n):
     """
     Splits a list into roughly n equal parts.

dejavu/database_sql.py

@@ -1,5 +1,5 @@
 from __future__ import absolute_import
-from itertools import izip_longest, ifilter
+from itertools import izip_longest
 import Queue
 
 import MySQLdb as mysql
@@ -312,7 +312,8 @@ class SQLDatabase(Database):
 
 def grouper(iterable, n, fillvalue=None):
     args = [iter(iterable)] * n
-    return (ifilter(None, values) for values in izip_longest(fillvalue=fillvalue, *args))
+    return (filter(None, values) for values
+            in izip_longest(fillvalue=fillvalue, *args))
 
 
 def cursor_factory(**factory_options):