Support __add__. Remove unnecessary syntatic sugar.

Author: MarcCote

nibabel/streamlines/tests/test_tractogram.py

@@ -187,7 +187,7 @@ def test_extend(self):
         sdict2 = PerArrayDict(len(DATA['tractogram']),
                               DATA['data_per_streamline'])
 
-        sdict += sdict2
+        sdict.extend(sdict2)
         assert_equal(len(sdict), len(sdict2))
         for k, v in DATA['tractogram'].data_per_streamline.items():
             assert_arrays_equal(sdict[k][:len(DATA['tractogram'])], v)
@@ -253,7 +253,7 @@ def test_extend(self):
         sdict = PerArraySequenceDict(total_nb_rows, DATA['data_per_point'])
         sdict2 = PerArraySequenceDict(total_nb_rows, DATA['data_per_point'])
 
-        sdict += sdict2
+        sdict.extend(sdict2)
         assert_equal(len(sdict), len(sdict2))
         for k, v in DATA['tractogram'].data_per_point.items():
             assert_arrays_equal(sdict[k][:len(DATA['tractogram'])], v)
@@ -602,9 +602,15 @@ def test_tractogram_to_world(self):
     def test_tractogram_extend(self):
         # Load tractogram that contains some metadata.
         t = DATA['tractogram'].copy()
-        new_t = DATA['tractogram'].copy()
 
         # Double the tractogram.
+        new_t = t + t
+        assert_equal(len(new_t), 2*len(t))
+        assert_tractogram_equal(new_t[:len(t)], DATA['tractogram'])
+        assert_tractogram_equal(new_t[len(t):], DATA['tractogram'])
+
+        # Double the tractogram inplace.
+        new_t = DATA['tractogram'].copy()
         new_t += t
         assert_equal(len(new_t), 2*len(t))
         assert_tractogram_equal(new_t[:len(t)], DATA['tractogram'])

nibabel/streamlines/tractogram.py

@@ -138,10 +138,6 @@ def extend(self, other):
         for key in self.keys():
             self[key] = np.concatenate([self[key], other[key]])
 
-    def __iadd__(self, other):
-        self.extend(other)
-        return self
-
 
 class PerArraySequenceDict(PerArrayDict):
     """ Dictionary for which key access can do slicing on the values.
@@ -192,10 +188,6 @@ def extend(self, other):
         for key in self.keys():
             self[key].extend(other[key])
 
-    def __iadd__(self, other):
-        self.extend(other)
-        return self
-
 
 class LazyDict(collections.MutableMapping):
     """ Dictionary of generator functions.
@@ -495,13 +487,18 @@ def extend(self, other):
         must match those contained in the other tractogram.
         """
         self.streamlines.extend(other.streamlines)
-        self.data_per_streamline += other.data_per_streamline
-        self.data_per_point += other.data_per_point
+        self.data_per_streamline.extend(other.data_per_streamline)
+        self.data_per_point.extend(other.data_per_point)
 
     def __iadd__(self, other):
         self.extend(other)
         return self
 
+    def __add__(self, other):
+        tractogram = self.copy()
+        tractogram += other
+        return tractogram
+
 
 class LazyTractogram(Tractogram):
     """ Lazy container for streamlines and their data information.