Add new composite dataset

docs/source/datasets.rst

@@ -5,4 +5,5 @@ Datasets
 
 .. autoclass:: FreeSoundSearch
 .. autoclass:: InternetArchive
-.. autoclass:: PhatDrumLoops
+.. autoclass:: PhatDrumLoops
+.. autoclass:: CompositeDataset

zounds/__init__.py

@@ -70,4 +70,4 @@
 
 from datasets import \
     PhatDrumLoops, InternetArchive, FreeSoundSearch, DataSetCache, Directory, \
-    ingest, MusicNet, NSynth
+    ingest, MusicNet, NSynth, CompositeDataset

zounds/datasets/__init__.py

@@ -14,3 +14,4 @@
 from ingest import ingest
 from predownload import PreDownload
 from nsynth import NSynth
+from composite import CompositeDataset

zounds/datasets/composite.py

@@ -0,0 +1,25 @@
+
+
+class CompositeDataset(object):
+    """
+    A dataset composed of two or more others
+
+    Args:
+        datasets (list of datasets): One or more other datasets
+
+    Examples:
+        >>> from zounds import InternetArchive, CompositeDataset, ingest
+        >>> dataset1 = InternetArchive('beethoven_ingigong_850')
+        >>> dataset2 = InternetArchive('The_Four_Seasons_Vivaldi-10361')
+        >>> composite = CompositeDataset(dataset1, dataset2)
+        >>> ingest(composite, Sound) # ingest data from both datasets
+    """
+
+    def __init__(self, *datasets):
+        super(CompositeDataset, self).__init__()
+        self.datasets = datasets
+
+    def __iter__(self):
+        for dataset in self.datasets:
+            for meta in dataset:
+                yield meta

zounds/datasets/test_composite.py

@@ -0,0 +1,34 @@
+import unittest2
+from predownload import PreDownload
+from composite import CompositeDataset
+from zounds.soundfile import AudioMetaData
+
+
+class DatasetA(object):
+    def __init__(self):
+        super(DatasetA, self).__init__()
+
+    def __iter__(self):
+        yield AudioMetaData(uri=PreDownload('', 'http://example.com/1'))
+        yield AudioMetaData(uri=PreDownload('', 'http://example.com/2'))
+
+
+class DatasetB(object):
+    def __init__(self):
+        super(DatasetB, self).__init__()
+
+    def __iter__(self):
+        yield AudioMetaData(uri=PreDownload('', 'http://example.com/3'))
+        yield AudioMetaData(uri=PreDownload('', 'http://example.com/4'))
+
+
+class CompositeDatasetTests(unittest2.TestCase):
+
+    def test_composite_iterates_over_multiple_datasets(self):
+        composite = CompositeDataset(DatasetA(), DatasetB())
+        items = [x.uri.url for x in composite]
+        self.assertEqual(4, len(items))
+        self.assertIn('http://example.com/1', items)
+        self.assertIn('http://example.com/2', items)
+        self.assertIn('http://example.com/3', items)
+        self.assertIn('http://example.com/4', items)