Revert ability to construct MultiIndex from empty arrays, ensure all tests pass despite issue pandas-dev#16844

Author: Douglas Rudd

pandas/core/indexes/multi.py

@@ -1083,7 +1083,9 @@ def from_arrays(cls, arrays, sortorder=None, names=None):
         MultiIndex.from_product : Make a MultiIndex from cartesian product
                                   of iterables
         """
-        if len(arrays) == 1:
+        if len(arrays) == 0:
+            raise ValueError('Must pass non-zero number of levels/labels')
+        elif len(arrays) == 1:
             name = None if names is None else names[0]
             return Index(arrays[0], name=name)
 
@@ -1131,10 +1133,12 @@ def from_tuples(cls, tuples, sortorder=None, names=None):
         MultiIndex.from_product : Make a MultiIndex from cartesian product
                                   of iterables
         """
-        if len(tuples) == 0 and names is None:
-            raise TypeError('Cannot infer number of levels from empty list')
-
-        if isinstance(tuples, (np.ndarray, Index)):
+        if len(tuples) == 0:
+            if names is None:
+                msg = 'Cannot infer number of levels from empty list'
+                raise TypeError(msg)
+            arrays = [[]]*len(names)
+        elif isinstance(tuples, (np.ndarray, Index)):
             if isinstance(tuples, Index):
                 tuples = tuples._values
 

pandas/tests/indexes/test_multi.py

@@ -766,14 +766,6 @@ def test_from_arrays_empty(self):
                 ValueError, "Must pass non-zero number of levels/labels"):
             MultiIndex.from_arrays(arrays=[])
 
-        # 0 levels, names defined
-        result = MultiIndex.from_arrays(arrays=[],
-                                        names=['A', 'B'])
-        expected = MultiIndex(levels=[[], []],
-                              labels=[[], []],
-                              names=['A', 'B'])
-        tm.assert_index_equal(result, expected)
-
         # 1 level
         result = MultiIndex.from_arrays(arrays=[[]], names=['A'])
         expected = Index([], name='A')
@@ -1726,9 +1718,8 @@ def test_from_tuples(self):
                                MultiIndex.from_tuples, [])
 
         result = MultiIndex.from_tuples([], names=['a', 'b'])
-        expected = MultiIndex(levels=[[], []],
-                              labels=[[], []],
-                              names=['a', 'b'])
+        expected = MultiIndex.from_arrays(arrays=[[], []],
+                                          names=['a', 'b'])
         tm.assert_index_equal(result, expected)
 
         idx = MultiIndex.from_tuples(((1, 2), (3, 4)), names=['a', 'b'])