perf?

Author: h-vetinari

pandas/core/strings.py

@@ -2139,12 +2139,15 @@ def cat(self, others=None, sep=None, na_rep=None, join=None):
         # if join is None, _get_series_list already aligned indexes
         join = 'left' if join is None else join
 
-        # Need to add keys for uniqueness in case of duplicate columns
-        others = concat(others, axis=1,
-                        join=(join if join == 'inner' else 'outer'),
-                        keys=range(len(others)))
-        data, others = data.align(others, join=join)
-        df = concat([data, others], axis=1).astype('object')
+        if any(not data.index.equals(x.index) for x in others):
+            # Need to add keys for uniqueness in case of duplicate columns
+            others = concat(others, axis=1,
+                            join=(join if join == 'inner' else 'outer'),
+                            keys=range(len(others)), copy=False)
+            data, others = data.align(others, join=join)
+            df = concat([data, others], axis=1, copy=False).astype('object')
+        else:
+            df = concat([data] + others, axis=1, copy=False).astype('object')
 
         # calculate in numpy using str_cat_core; result is 1-dim np.ndarray
         if na_rep is None: