Forward slicing in DataIO (#141)

* Forward slicing in DataIO 
* Fix #144 by adding copy/deepcopy to DataIO
* Add testing for DataIO

src/hdmf/data_utils.py

@@ -9,6 +9,7 @@
 import numpy as np
 from warnings import warn
 from six import with_metaclass, text_type, binary_type
+import copy
 
 from .container import Data, DataRegion
 from .utils import docval, getargs, popargs, docval_macro, get_data_shape
@@ -563,6 +564,15 @@ def __init__(self, **kwargs):
     def data(self):
         return self.__data
 
+    def __copy__(self):
+        newobj = DataIO(data=self.data)
+        return newobj
+
+    def __deepcopy__(self, memo):
+        result = DataIO(data=copy.deepcopy(self.__data))
+        memo[id(self)] = result
+        return result
+
     def __len__(self):
         if not self.valid:
             raise InvalidDataIOError("Cannot get length of data. Data is not valid.")
@@ -577,6 +587,12 @@ def __getattr__(self, attr):
             raise InvalidDataIOError("Cannot get attribute '%s' of data. Data is not valid." % attr)
         return getattr(self.data, attr)
 
+    def __getitem__(self, item):
+        """Delegate slicing to the data object"""
+        if not self.valid:
+            raise InvalidDataIOError("Cannot get item from data. Data is not valid.")
+        return self.data[item]
+
     def __array__(self):
         """
         Support conversion of DataIO.data to a numpy array. This function is

tests/unit/utils_test/test_core_DataIO.py

@@ -0,0 +1,39 @@
+import unittest2 as unittest
+
+from hdmf.data_utils import DataIO
+import numpy as np
+from copy import copy, deepcopy
+
+
+class DataIOTests(unittest.TestCase):
+
+    def setUp(self):
+        pass
+
+    def tearDown(self):
+        pass
+
+    def test_copy(self):
+        obj = DataIO(data=[1., 2., 3.])
+        obj_copy = copy(obj)
+        self.assertNotEqual(id(obj), id(obj_copy))
+        self.assertEqual(id(obj.data), id(obj_copy.data))
+
+    def test_deepcopy(self):
+        obj = DataIO(data=[1., 2., 3.])
+        obj_copy = deepcopy(obj)
+        self.assertNotEqual(id(obj), id(obj_copy))
+        self.assertNotEqual(id(obj.data), id(obj_copy.data))
+
+    def test_dataio_slice_delegation(self):
+        indata = np.arange(30)
+        dset = DataIO(indata)
+        self.assertTrue(np.all(dset[2:15] == indata[2:15]))
+
+        indata = np.arange(50).reshape(5, 10)
+        dset = DataIO(indata)
+        self.assertTrue(np.all(dset[1:3, 5:8] == indata[1:3, 5:8]))
+
+
+if __name__ == '__main__':
+    unittest.main()