HDFStore: Fix empty result of keys() method on non-pandas hdf5 file

An additional kind parameter has been added that defaults to pandas
original behavior, but with 'tables' value gives you the list of
non-pandas tables in the file

Author: roberthdevries

pandas/io/pytables.py

@@ -590,16 +590,33 @@ def __enter__(self):
     def __exit__(self, exc_type, exc_value, traceback):
         self.close()
 
-    def keys(self) -> List[str]:
+    def keys(self, kind='pandas') -> List[str]:
         """
         Return a list of keys corresponding to objects stored in HDFStore.
 
+        Parameters
+        ----------
+        kind : str, default 'pandas'
+                When kind equals 'pandas' return pandas objects
+                When kind equals 'table' return Tables
+                Otherwise fail with a ValueError
+
+        Raises
+        ------
+        raises ValueError if kind has an illegal value
+
         Returns
         -------
         list
             List of ABSOLUTE path-names (e.g. have the leading '/').
         """
-        return [n._v_pathname for n in self.groups()]
+        if kind == 'pandas':
+            return [n._v_pathname for n in self.groups()]
+
+        if kind == 'tables':
+            self._check_if_open()
+            return [n._v_pathname for n in self._handle.walk_nodes('/', classname='Table')]
+        raise ValueError(f"kind should be either pandas' or 'table' but is {kind}")
 
     def __iter__(self):
         return iter(self.keys())

pandas/tests/io/pytables/test_store.py

@@ -298,6 +298,26 @@ def test_keys(self, setup_path):
             assert set(store.keys()) == expected
             assert set(store) == expected
 
+    def test_non_pandas_keys(self, setup_path):
+
+        class Table1(tables.IsDescription):
+            value1 = tables.Float32Col()
+        class Table2(tables.IsDescription):
+            value2 = tables.Float32Col()
+        class Table3(tables.IsDescription):
+            value3 = tables.Float32Col()
+        with ensure_clean_path(setup_path) as path:
+            with tables.open_file(path, mode="w") as h5file:
+                group = h5file.create_group("/", "group")
+                table1 = h5file.create_table(group, "table1", Table1, "Table 1")
+                table2 = h5file.create_table(group, "table2", Table2, "Table 2")
+                table3 = h5file.create_table(group, "table3", Table3, "Table 3")
+            with HDFStore(path) as store:
+                assert len(store.keys(kind="tables")) == 3
+                expected = {"/group/table1", "/group/table2", "/group/table3"}
+                assert set(store.keys(kind="tables")) == expected
+                assert set(store) == set()
+
     def test_keys_ignore_hdf_softlink(self, setup_path):
 
         # GH 20523