BUG: fillna ignoring axis=1 parameter. pandas-dev#17399

Author: pratapvardhan

pandas/core/generic.py

@@ -4136,9 +4136,14 @@ def fillna(self, value=None, method=None, axis=None, inplace=False,
                 return result if not inplace else None
 
             elif not is_list_like(value):
-                new_data = self._data.fillna(value=value, limit=limit,
+                if axis == 0:
+                    new_data = self._data.fillna(value=value, limit=limit,
+                                                 inplace=inplace,
+                                                 downcast=downcast)
+                elif axis == 1:
+                    new_data = self.T.fillna(value=value, limit=limit,
                                              inplace=inplace,
-                                             downcast=downcast)
+                                             downcast=downcast).T._data
             elif isinstance(value, DataFrame) and self.ndim == 2:
                 new_data = self.where(self.notna(), value)
             else:

pandas/tests/frame/test_missing.py

@@ -388,6 +388,14 @@ def test_frame_fillna_limit(self):
         expected.values[:3] = np.nan
         tm.assert_frame_equal(result, expected)
 
+        # axis=1
+        # GH 7399
+        df.iloc[1:4, 1:4] = nan
+        expected = df.copy()
+        expected.iloc[1:4, 1:3] = 0
+        result = df.fillna(0, limit=2, axis=1)
+        tm.assert_frame_equal(result, expected)
+
     def test_fillna_skip_certain_blocks(self):
         # don't try to fill boolean, int blocks