Fixed Value Error when doing HDFStore.Select of contiguous mixed-data (#17670)

Author: amolkahat

doc/source/whatsnew/v0.21.0.txt

@@ -603,6 +603,7 @@ I/O
 - Bug in :func:`read_html` where import check fails when run in multiple threads (:issue:`16928`)
 - Bug in :func:`read_csv` where automatic delimiter detection caused a ``TypeError`` to be thrown when a bad line was encountered rather than the correct error message (:issue:`13374`)
 - Bug in ``DataFrame.to_html()`` with ``notebook=True`` where DataFrames with named indices or non-MultiIndex indices had undesired horizontal or vertical alignment for column or row labels, respectively (:issue:`16792`)
+- Bug in :func:`HDFStore.select` when reading a contiguous mixed-data table featuring VLArray (:issue:`17021`)
 
 Plotting
 ^^^^^^^^

pandas/io/pytables.py

@@ -2441,13 +2441,12 @@ def read_array(self, key, start=None, stop=None):
  """ read an array for the specified node (off of group """
  import tables
  node = getattr(self.group, key)
- data = node[start:stop]
  attrs = node._v_attrs
 
  transposed = getattr(attrs, 'transposed', False)
 
  if isinstance(node, tables.VLArray):
- ret = data[0]
+ ret = node[0][start:stop]
  else:
  dtype = getattr(attrs, 'value_type', None)
  shape = getattr(attrs, 'shape', None)
@@ -2456,7 +2455,7 @@ def read_array(self, key, start=None, stop=None):
  # length 0 axis
  ret = np.empty(shape, dtype=dtype)
  else:
- ret = data
+ ret = node[start:stop]
 
  if dtype == u('datetime64'):
 

pandas/tests/io/test_pytables.py

@@ -4391,6 +4391,19 @@ def test_path_pathlib(self):
  lambda p: pd.read_hdf(p, 'df'))
  tm.assert_frame_equal(df, result)
 
+ @pytest.mark.parametrize('start, stop', [(0, 2), (1, 2), (None, None)])
+ def test_contiguous_mixed_data_table(self, start, stop):
+ # GH 17021
+ # ValueError when reading a contiguous mixed-data table ft. VLArray
+ df = DataFrame({'a': Series([20111010, 20111011, 20111012]),
+ 'b': Series(['ab', 'cd', 'ab'])})
+
+ with ensure_clean_store(self.path) as store:
+ store.append('test_dataset', df)
+
+ result = store.select('test_dataset', start=start, stop=stop)
+ assert_frame_equal(df[start:stop], result)
+
  def test_path_pathlib_hdfstore(self):
  df = tm.makeDataFrame()