API: raise notImplementedError on to_json(orient='table') for a DataFrame with a column MultiIndex (#16095)

closes #15996

Author: jreback

pandas/io/json/json.py

@@ -6,7 +6,7 @@
 from pandas._libs.tslib import iNaT
 from pandas.compat import StringIO, long, u
 from pandas import compat, isnull
-from pandas import Series, DataFrame, to_datetime
+from pandas import Series, DataFrame, to_datetime, MultiIndex
 from pandas.io.common import get_filepath_or_buffer, _get_handle
 from pandas.core.common import AbstractMethodError
 from pandas.io.formats.printing import pprint_thing
@@ -138,6 +138,11 @@ def __init__(self, obj, orient, date_format, double_precision,
 
         self.schema = build_table_schema(obj)
 
+        # NotImplementd on a column MultiIndex
+        if obj.ndim == 2 and isinstance(obj.columns, MultiIndex):
+            raise NotImplementedError(
+                "orient='table' is not supported for MultiIndex")
+
         # TODO: Do this timedelta properly in objToJSON.c See GH #15137
         if ((obj.ndim == 1) and (obj.name in set(obj.index.names)) or
                 len(obj.columns & obj.index.names)):

pandas/tests/io/formats/test_printing.py

@@ -1,7 +1,10 @@
 # -*- coding: utf-8 -*-
 import pytest
-from pandas import compat
+
+import numpy as np
 import pandas as pd
+
+from pandas import compat
 import pandas.io.formats.printing as printing
 import pandas.io.formats.format as fmt
 import pandas.util.testing as tm
@@ -166,6 +169,18 @@ def test_publishes(self):
                     'application/vnd.dataresource+json'}
         self.assertEqual(set(arg.keys()), expected)
 
+    def test_publishes_not_implemented(self):
+        # column MultiIndex
+        # GH 15996
+        midx = pd.MultiIndex.from_product([['A', 'B'], ['a', 'b', 'c']])
+        df = pd.DataFrame(np.random.randn(5, len(midx)), columns=midx)
+
+        make_patch = self.mock.patch('IPython.display.display')
+        opt = pd.option_context('display.html.table_schema', True)
+        with opt, make_patch as mock_display:  # noqa
+            with pytest.raises(NotImplementedError):
+                df._ipython_display_()
+
     def test_config_on(self):
         df = pd.DataFrame({"A": [1, 2]})
         with pd.option_context("display.html.table_schema", True):