Fix bug where use of .ix[tuple(...)]=x fails to correctly check out of bounds index for columns. This is a regression as it used to work in pandas 0.12.0. The code incorrectly checks the column index against the len() of the dataframe to see if it is in bounds not against the number of columns. Have added 2 tests with non-square dataframes to test that the fix works.

Author: Andrew Burrows

pandas/core/indexing.py

@@ -903,7 +903,8 @@ def _convert_to_indexer(self, obj, axis=0, is_setter=False):
                     return {'key': obj}
 
                 # a positional
-                if obj >= len(self.obj) and not isinstance(labels, MultiIndex):
+                if (obj >= self.obj.shape[axis] and
+                        not isinstance(labels, MultiIndex)):
                     raise ValueError("cannot set by positional indexing with "
                                      "enlargement")
 

pandas/tests/test_indexing.py

@@ -2352,6 +2352,14 @@ def check_slicing_positional(index):
         #self.assertRaises(TypeError, lambda : s.iloc[2.0:5.0])
         #self.assertRaises(TypeError, lambda : s.iloc[2:5.0])
 
+    def test_set_ix_out_of_bounds_axis_0(self):
+        df = pd.DataFrame(randn(2, 5), index=["row%s" % i for i in range(2)], columns=["col%s" % i for i in range(5)])
+        self.assertRaises(ValueError, df.ix.__setitem__, (2, 0), 100)
+
+    def test_set_ix_out_of_bounds_axis_1(self):
+        df = pd.DataFrame(randn(5, 2), index=["row%s" % i for i in range(5)], columns=["col%s" % i for i in range(2)])
+        self.assertRaises(ValueError, df.ix.__setitem__, (0 , 2), 100)
+
 
 if __name__ == '__main__':
     import nose