BUG: to_records() fails for MultiIndex DF (#21064)

pandas-dev · May 23, 2018 · f89e883 · f89e883
1 parent a327920
commit f89e883
Show file tree

Hide file tree

Showing 3 changed files with 40 additions and 2 deletions.
diff --git a/doc/source/whatsnew/v0.24.0.txt b/doc/source/whatsnew/v0.24.0.txt
@@ -131,7 +131,7 @@ Indexing
 MultiIndex
 ^^^^^^^^^^
 
--
+- Bug :func:`to_records` fails for empty MultiIndex DF (:issue:`21064`)
 -
 -
 

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
@@ -1392,7 +1392,13 @@ def to_records(self, index=True, convert_datetime64=None):
             else:
                 if isinstance(self.index, MultiIndex):
                     # array of tuples to numpy cols. copy copy copy
-                    ix_vals = lmap(np.array, zip(*self.index.values))
+                    tuples = self.index.values
+                    if len(tuples):
+                        ix_vals = lmap(np.array, zip(*tuples))
+                    else:
+                        # empty MultiIndex DF
+                        ix_vals = [np.array([], dtype=lev.dtype)
+                                   for lev in self.index.levels]
                 else:
                     ix_vals = [self.index.values]
 

diff --git a/pandas/tests/frame/test_convert_to.py b/pandas/tests/frame/test_convert_to.py
@@ -328,3 +328,35 @@ def test_to_dict_index_dtypes(self, into, expected):
         result = DataFrame.from_dict(result, orient='index')[cols]
         expected = DataFrame.from_dict(expected, orient='index')[cols]
         tm.assert_frame_equal(result, expected)
+
+    def test_to_records_with_multiindex(self):
+        size = 4
+        idx1 = [u'a', u'a', u'b', u'b']
+        idx2 = [u'x', u'y', u'x', u'y']
+        tup = zip(idx1, idx2)
+        index = MultiIndex.from_tuples(tup)
+        random_data = np.random.randn(size, size)
+        df = DataFrame(random_data, index=index)
+
+        result = df.to_records(index=True)
+
+        col_arrays = [idx1, idx2] + [col for col in random_data.T]
+        expected = np.rec.fromarrays(
+            col_arrays, dtype=np.dtype([('level_0', '<U1'), ('level_1', '<U1'),
+                                        ('0', '<f8'), ('1', '<f8'),
+                                        ('2', '<f8'), ('3', '<f8')]))
+
+        tm.assert_numpy_array_equal(result, expected)
+
+    def test_to_records_with_empty_multiindex(self):
+        # GH 21064
+        multi = MultiIndex([['a'], ['b']], labels=[[], []])
+        df = DataFrame(columns=['A'], index=multi)
+
+        expected = np.rec.fromarrays([[], [], []],
+                                     dtype=np.dtype([('level_0', 'O'),
+                                                     ('level_1', 'O'),
+                                                     ('A', 'O')]))
+
+        result = df.to_records(index=True)
+        tm.assert_numpy_array_equal(result, expected)