Fix DataBatch.__str__ for cases where we don't have labels.

python/mxnet/io.py

@@ -168,7 +168,10 @@ def __init__(self, data, label=None, pad=None, index=None,
 
     def __str__(self):
         data_shapes = [d.shape for d in self.data]
-        label_shapes = [l.shape for l in self.label]
+        if self.label:
+            label_shapes = [l.shape for l in self.label]
+        else:
+            label_shapes = None
         return "{}: data shapes: {} label shapes: {}".format(
             self.__class__.__name__,
             data_shapes,

tests/python/unittest/test_io.py

@@ -252,6 +252,17 @@ def check_libSVMIter_news_data():
     check_libSVMIter_synthetic()
     check_libSVMIter_news_data()
 
+
+def test_DataBatch():
+    from nose.tools import ok_
+    from mxnet.io import DataBatch
+    import re
+    batch = DataBatch(data=[mx.nd.ones((2,3))])
+    ok_(re.match('DataBatch: data shapes: \[\(2L?, 3L?\)\] label shapes: None', str(batch)))
+    batch = DataBatch(data=[mx.nd.ones((2,3)), mx.nd.ones((7,8))], label=[mx.nd.ones((4,5))])
+    ok_(re.match('DataBatch: data shapes: \[\(2L?, 3L?\), \(7L?, 8L?\)\] label shapes: [(4, 5)]', str(batch)))
+
+
 @unittest.skip("test fails intermittently. temporarily disabled till it gets fixed. tracked at https://github.com/apache/incubator-mxnet/issues/7826")
 def test_CSVIter():
     def check_CSVIter_synthetic():