BUG: missing case for assigning DataFrame via ix

Author: Chang She

pandas/core/indexing.py

@@ -180,6 +180,15 @@ def _align_frame(self, indexer, df):
                     val = df.reindex(idx, columns=cols).values
                 return val
 
+        elif ((isinstance(indexer, slice) or com.is_list_like(indexer))
+              and is_frame):
+            ax = self.obj.index[indexer]
+            if df.index.equals(ax):
+                val = df.copy().values
+            else:
+                val = df.reindex(ax).values
+            return val
+
         elif np.isscalar(indexer) and not is_frame:
             idx = self.obj.axes[1]
             cols = self.obj.axes[2]

pandas/tests/test_frame.py

@@ -726,6 +726,26 @@ def test_ix_align(self):
         s = dft.ix[0, idx]
         assert_series_equal(s, b.reindex(s.index))
 
+    def test_ix_frame_align(self):
+        b = DataFrame(np.random.randn(3, 4))
+        df_orig = DataFrame(randn(10, 4))
+        df = df_orig.copy()
+
+        df.ix[:3] = b
+        out = b.ix[:3]
+        assert_frame_equal(out, b)
+
+        b.sort_index(inplace=True)
+        df = df_orig.copy()
+        df.ix[[0, 1, 2]] = b
+        out = df.ix[[0, 1, 2]].reindex(b.index)
+        assert_frame_equal(out, b)
+
+        df = df_orig.copy()
+        df.ix[:3] = b
+        out = df.ix[:3]
+        assert_frame_equal(out, b.reindex(out.index))
+
     def test_getitem_setitem_non_ix_labels(self):
         df = tm.makeTimeDataFrame()