Merge pull request #10401 from kawochen/BUG-FIX-10392

BUG: GH10392 bug where Table.select_column does not preserve column name

Author: jreback

doc/source/whatsnew/v0.17.0.txt

@@ -74,3 +74,4 @@ Bug Fixes
 - Bug in ``pd.Series`` when setting a value on an empty ``Series`` whose index has a frequency. (:issue:`10193`)
 - Bug in ``DataFrame.reset_index`` when index contains `NaT`. (:issue:`10388`)
 - Bug in ``ExcelReader`` when worksheet is empty (:issue:`6403`)
+- Bug in ``Table.select_column`` where name is not preserved (:issue:`10392`)

pandas/io/pytables.py

@@ -3608,7 +3608,7 @@ def read_column(self, column, where=None, start=None, stop=None, **kwargs):
                                                 nan_rep=self.nan_rep,
                                                 encoding=self.encoding
                                                 ).take_data(),
-                                      a.tz, True))
+                                      a.tz, True), name=column)
 
         raise KeyError("column [%s] not found in the table" % column)
 

pandas/io/tests/test_pytables.py

@@ -3766,7 +3766,7 @@ def f():
             # valid
             result = store.select_column('df', 'index')
             tm.assert_almost_equal(result.values, Series(df.index).values)
-            self.assertIsInstance(result,Series)
+            self.assertIsInstance(result, Series)
 
             # not a data indexable column
             self.assertRaises(
@@ -3806,6 +3806,14 @@ def f():
             result = store.select_column('df3', 'string', start=-2, stop=2)
             tm.assert_almost_equal(result.values, df3['string'].values[-2:2])
 
+            # GH 10392 - make sure column name is preserved
+            df4 = DataFrame({'A': np.random.randn(10), 'B': 'foo'})
+            store.append('df4', df4, data_columns=True)
+            expected = df4['B']
+            result = store.select_column('df4', 'B')
+            tm.assert_series_equal(result, expected)
+
+
     def test_coordinates(self):
         df = tm.makeTimeDataFrame()