DOC: add data_columns to doc string of df.to_hdf() and HDFStore.append() (#14046)

Author: jorisvandenbossche

pandas/core/generic.py

@@ -1105,18 +1105,20 @@ def to_hdf(self, path_or_buf, key, **kwargs):
               and if the file does not exist it is created.
           ``'r+'``
               It is similar to ``'a'``, but the file must already exist.
-        format   : 'fixed(f)|table(t)', default is 'fixed'
+        format : 'fixed(f)|table(t)', default is 'fixed'
             fixed(f) : Fixed format
                        Fast writing/reading. Not-appendable, nor searchable
             table(t) : Table format
                        Write as a PyTables Table structure which may perform
                        worse but allow more flexible operations like searching
                        / selecting subsets of the data
-        append   : boolean, default False
+        append : boolean, default False
             For Table formats, append the input data to the existing
-        data_columns : list of columns to create as data columns, or True to
-            use all columns. See
-            `here <http://pandas.pydata.org/pandas-docs/stable/io.html#query-via-data-columns>`__ # noqa
+        data_columns :  list of columns, or True, default None
+            List of columns to create as indexed data columns for on-disk
+            queries, or True to use all columns. By default only the axes
+            of the object are indexed. See `here
+            <http://pandas.pydata.org/pandas-docs/stable/io.html#query-via-data-columns>`__.
 
             Applicable only to format='table'.
         complevel : int, 1-9, default 0

pandas/io/pytables.py

@@ -938,9 +938,11 @@ def append(self, key, value, format=None, append=True, columns=None,
                        / selecting subsets of the data
         append       : boolean, default True, append the input data to the
             existing
-        data_columns : list of columns to create as data columns, or True to
-            use all columns. See
-            `here <http://pandas.pydata.org/pandas-docs/stable/io.html#query-via-data-columns>`__ # noqa
+        data_columns :  list of columns, or True, default None
+            List of columns to create as indexed data columns for on-disk
+            queries, or True to use all columns. By default only the axes
+            of the object are indexed. See `here
+            <http://pandas.pydata.org/pandas-docs/stable/io.html#query-via-data-columns>`__.
         min_itemsize : dict of columns that specify minimum string sizes
         nan_rep      : string to use as string nan represenation
         chunksize    : size to chunk the writing