BUG: Validate levels in a multi-index before storing in a HDFStore (GH5527)

doc/source/release.rst

@@ -549,6 +549,7 @@ Bug Fixes
     - A zero length series written in Fixed format not deserializing properly.
       (:issue:`4708`)
     - Fixed decoding perf issue on pyt3 (:issue:`5441`)
+    - Validate levels in a multi-index before storing (:issue:`5527`)
   - Fixed bug in tslib.tz_convert(vals, tz1, tz2): it could raise IndexError
     exception while trying to access trans[pos + 1] (:issue:`4496`)
   - The ``by`` argument now works correctly with the ``layout`` argument

pandas/io/pytables.py

@@ -2688,6 +2688,14 @@ def is_multi_index(self):
         """ the levels attribute is 1 or a list in the case of a multi-index """
         return isinstance(self.levels,list)
 
+    def validate_multiindex(self, obj):
+        """ validate that we can store the multi-index; reset and return the new object """
+        levels = [ l if l is not None else "level_{0}".format(i) for i, l in enumerate(obj.index.names) ]
+        try:
+            return obj.reset_index(), levels
+        except (ValueError):
+            raise ValueError("duplicate names/columns in the multi-index when storing as a table")
+
     @property
     def nrows_expected(self):
         """ based on our axes, compute the expected nrows """
@@ -3701,10 +3709,9 @@ class AppendableMultiSeriesTable(AppendableSeriesTable):
     def write(self, obj, **kwargs):
         """ we are going to write this as a frame table """
         name = obj.name or 'values'
-        cols = list(obj.index.names)
+        obj, self.levels = self.validate_multiindex(obj)
+        cols = list(self.levels)
         cols.append(name)
-        self.levels = list(obj.index.names)
-        obj = obj.reset_index()
         obj.columns = cols
         return super(AppendableMultiSeriesTable, self).write(obj=obj, **kwargs)
 
@@ -3764,6 +3771,7 @@ class AppendableMultiFrameTable(AppendableFrameTable):
     table_type = u('appendable_multiframe')
     obj_type = DataFrame
     ndim = 2
+    _re_levels = re.compile("^level_\d+$")
 
     @property
     def table_type_short(self):
@@ -3774,11 +3782,11 @@ def write(self, obj, data_columns=None, **kwargs):
             data_columns = []
         elif data_columns is True:
             data_columns = obj.columns[:]
-        for n in obj.index.names:
+        obj, self.levels = self.validate_multiindex(obj)
+        for n in self.levels:
             if n not in data_columns:
                 data_columns.insert(0, n)
-        self.levels = obj.index.names
-        return super(AppendableMultiFrameTable, self).write(obj=obj.reset_index(), data_columns=data_columns, **kwargs)
+        return super(AppendableMultiFrameTable, self).write(obj=obj, data_columns=data_columns, **kwargs)
 
     def read(self, columns=None, **kwargs):
         if columns is not None:
@@ -3787,7 +3795,11 @@ def read(self, columns=None, **kwargs):
                     columns.insert(0, n)
         df = super(AppendableMultiFrameTable, self).read(
             columns=columns, **kwargs)
-        df.set_index(self.levels, inplace=True)
+        df = df.set_index(self.levels)
+
+        # remove names for 'level_%d'
+        df.index = df.index.set_names([ None if self._re_levels.search(l) else l for l in df.index.names ])
+
         return df
 
 

pandas/io/tests/test_pytables.py

@@ -1572,6 +1572,51 @@ def test_column_multiindex(self):
             store.put('df1',df,format='table')
             tm.assert_frame_equal(store['df1'],df,check_index_type=True,check_column_type=True)
 
+    def test_store_multiindex(self):
+
+        # validate multi-index names
+        # GH 5527
+        with ensure_clean_store(self.path) as store:
+
+            def make_index(names=None):
+                return MultiIndex.from_tuples([( datetime.datetime(2013,12,d), s, t) for d in range(1,3) for s in range(2) for t in range(3)],
+                                              names=names)
+
+
+            # no names
+            _maybe_remove(store, 'df')
+            df = DataFrame(np.zeros((12,2)), columns=['a','b'], index=make_index())
+            store.append('df',df)
+            tm.assert_frame_equal(store.select('df'),df)
+
+            # partial names
+            _maybe_remove(store, 'df')
+            df = DataFrame(np.zeros((12,2)), columns=['a','b'], index=make_index(['date',None,None]))
+            store.append('df',df)
+            tm.assert_frame_equal(store.select('df'),df)
+
+            # series
+            _maybe_remove(store, 's')
+            s = Series(np.zeros(12), index=make_index(['date',None,None]))
+            store.append('s',s)
+            tm.assert_series_equal(store.select('s'),s)
+
+            # dup with column
+            _maybe_remove(store, 'df')
+            df = DataFrame(np.zeros((12,2)), columns=['a','b'], index=make_index(['date','a','t']))
+            self.assertRaises(ValueError, store.append, 'df',df)
+
+            # dup within level
+            _maybe_remove(store, 'df')
+            df = DataFrame(np.zeros((12,2)), columns=['a','b'], index=make_index(['date','date','date']))
+            self.assertRaises(ValueError, store.append, 'df',df)
+
+            # fully names
+            _maybe_remove(store, 'df')
+            df = DataFrame(np.zeros((12,2)), columns=['a','b'], index=make_index(['date','s','t']))
+            store.append('df',df)
+            tm.assert_frame_equal(store.select('df'),df)
+
     def test_pass_spec_to_storer(self):
 
         df = tm.makeDataFrame()