BUG: Fix bug for unstack with a lot of indices (pandas-dev#32624)

Author: patrick

pandas/core/reshape/reshape.py

@@ -363,7 +363,7 @@ def _unstack_multiple(data, clocs, fill_value=None):
             for i in range(len(clocs)):
                 val = clocs[i]
                 result = result.unstack(val, fill_value=fill_value)
-                clocs = [v if i > v else v - 1 for v in clocs]
+                clocs = [v if v < val else v - 1 for v in clocs]
 
             return result
 

pandas/tests/frame/test_reshape.py

@@ -765,6 +765,19 @@ def test_unstack_unused_level(self, cols):
         expected.index = expected.index.droplevel("C")
         tm.assert_frame_equal(result, expected)
 
+    def test_unstack_long_index(self):
+        # PH 32624: Error when using a lot of indices to unstack. The error occurred only, if a lot of indices are used.
+        df = pd.DataFrame([[1]],
+                          columns=pd.MultiIndex.from_tuples([[0]], names=['c1']),
+                          index=pd.MultiIndex.from_tuples([[0, 0, 1, 0, 0, 0, 1]],
+                                                          names=['i1', 'i2', 'i3', 'i4', 'i5', 'i6', 'i7']))
+        result = df.unstack(["i2", "i3", "i4", "i5", "i6", "i7"])
+        expected = pd.DataFrame([[1]],
+                                columns=pd.MultiIndex.from_tuples([[0, 0, 1, 0, 0, 0, 1]],
+                                                                  names=['c1', 'i2', 'i3', 'i4', 'i5', 'i6', 'i7']),
+                                index=pd.Index([0], name='i1'))
+        tm.assert_frame_equal(result, expected)
+
     def test_unstack_nan_index(self):  # GH7466
         def cast(val):
             val_str = "" if val != val else val