Refactor multiindex unmerging to be cleaner

Author: tomneep

pandas/io/formats/format.py

@@ -904,37 +904,34 @@ def get_col_type(dtype):
 
         # reestablish the MultiIndex that has been joined by _to_str_column
         if self.fmt.index and isinstance(self.frame.index, MultiIndex):
+            out = self.frame.index.format(
+                adjoin=False, sparsify=self.fmt.sparsify,
+                names=any(self.frame.index.names), na_rep=self.fmt.na_rep
+            )
+
+            # index.format will sparsify repeated entries with empty strings
+            # so pad these with some empty space
+            def pad_empties(x):
+                for pad in x[::-1]:
+                    if pad:
+                        break
+                return [x[0]] + [i if i else ' ' * len(pad) for i in x[1:]]
+            out = (pad_empties(x) for x in out)
+
+            # Add empty spaces for each column level
             clevels = self.frame.columns.nlevels
+            out = [[' ' * len(x[-1])] * clevels + x for x in out]
+
+            # Add the column names to the last index column
+            cnames = self.frame.columns.names
+            if any(cnames):
+                new_names = [i if i else '{}' for i in cnames]
+                out[self.frame.index.nlevels - 1][:clevels] = new_names
+
+            # Get rid of old multiindex column and add new ones
             strcols.pop(0)
-            name = any(self.frame.index.names)
-            cname = any(self.frame.columns.names)
-            lastcol = self.frame.index.nlevels - 1
-            previous_lev3 = None
-            for i, lev in enumerate(self.frame.index.levels):
-                lev2 = lev.format()
-                blank = (' ' * len(lev2[0]) if lev2 else
-                         ' ' * len(self.fmt.na_rep))
-                # display column names in last index-column
-                if cname and i == lastcol:
-                    lev3 = [x if x else '{}' for x in self.frame.columns.names]
-                else:
-                    lev3 = [blank] * clevels
-                if name:
-                    lev3.append(lev.name)
-                current_idx_val = None
-                for level_idx in self.frame.index.labels[i]:
-                    idx_val = (lev2[level_idx] if level_idx >= 0 else
-                               self.fmt.na_rep)
-                    if ((previous_lev3 is None or
-                         previous_lev3[len(lev3)].isspace()) and
-                            idx_val == current_idx_val):
-                        # same index as above row and left index was the same
-                        lev3.append(blank)
-                    else:
-                        lev3.append(idx_val)
-                        current_idx_val = idx_val
-                strcols.insert(i, lev3)
-                previous_lev3 = lev3
+            for i, o in enumerate(out):
+                strcols.insert(i, o)
 
         column_format = self.column_format
         if column_format is None: