BUG: Allow concat to take string axis names

Adding tests for concat string axis names

Fixing pep8 related spacing

doc/source/whatsnew/v0.19.1.txt

@@ -44,4 +44,5 @@ Bug Fixes
 
 
 - Bug in ``pd.concat`` where names of the ``keys`` were not propagated to the resulting ``MultiIndex`` (:issue:`14252`)
+- Bug in ``pd.concat`` where ``axis`` cannot take string parameters ``rows`` or ``columns (:issue:`14369`)
 - Bug in ``MultiIndex.set_levels`` where illegal level values were still set after raising an error (:issue:`13754`)

pandas/tests/frame/test_combine_concat.py

@@ -347,6 +347,20 @@ def test_concat_named_keys(self):
                                              names=[None, None]))
         assert_frame_equal(concatted_unnamed, expected_unnamed)
 
+    def test_concat_axis_parameter(self):
+        # GH 14369
+        df1 = pd.DataFrame({'A': [0.1, 0.2]}, index=range(2))
+        df2 = pd.DataFrame({'A': [0.3, 0.4]}, index=range(2))
+        expected_row = pd.DataFrame(
+            {'A': [0.1, 0.2, 0.3, 0.4]}, index=[0, 1, 0, 1])
+        concatted_row = pd.concat([df1, df2], axis='rows')
+        assert_frame_equal(concatted_row, expected_row)
+
+        expected_columns = pd.DataFrame(
+            [[0.1, 0.3], [0.2, 0.4]], index=[0, 1], columns=['A', 'A'])
+        concatted_columns = pd.concat([df1, df2], axis='columns')
+        assert_frame_equal(concatted_columns, expected_columns)
+
 
 class TestDataFrameCombineFirst(tm.TestCase, TestData):
 

pandas/tools/merge.py

@@ -1283,7 +1283,7 @@ def concat(objs, axis=0, join='outer', join_axes=None, ignore_index=False,
         argument, unless it is passed, in which case the values will be
         selected (see below). Any None objects will be dropped silently unless
         they are all None in which case a ValueError will be raised
-    axis : {0, 1, ...}, default 0
+    axis : {0, 1, 'rows', 'columns', ...}, default 0
         The axis to concatenate along
     join : {'inner', 'outer'}, default 'outer'
         How to handle indexes on other axis(es)
@@ -1411,6 +1411,10 @@ def __init__(self, objs, axis=0, join='outer', join_axes=None,
             sample = objs[0]
         self.objs = objs
 
+        # Check for string axis parameter
+        if isinstance(axis, str):
+            axis = objs[0]._get_axis_number(axis)
+
         # Need to flip BlockManager axis in the DataFrame special case
         self._is_frame = isinstance(sample, DataFrame)
         if self._is_frame: