correct

Author: zhangbowen-coder

pandas/core/reshape/merge.py

@@ -225,13 +225,29 @@ def merge(
     sort : bool, default False
         Sort the join keys lexicographically in the result DataFrame. If False,
         the order of the join keys depends on the join type (how keyword).
+    diff_option : Literal str
+        The allowed values are "suffix"、"prefix"、"both",default "suffix".
+        If the value is "suffix", the duplicated columns will be differentiated
+        using the suffixes provided by parameter "suffixes".
+        If the value is "prefix", the duplicated columns will be differentiated
+        using the prefixes provided by parameter "prefixes".
+        If the value is "both", the duplicated columns will be differentiated
+        using both the suffixes provided by parameter "suffixes" and
+        the prefixes provided by parameter "prefixes".
     suffixes : list-like, default is ("_x", "_y")
         A length-2 sequence where each element is optionally a string
         indicating the suffix to add to overlapping column names in
         `left` and `right` respectively. Pass a value of `None` instead
         of a string to indicate that the column name from `left` or
         `right` should be left as-is, with no suffix. At least one of the
         values must not be None.
+    prefixes : list-like, default is ("a_", "b_")
+        A length-2 sequence where each element is optionally a string
+        indicating the prefix to add to overlapping column names in
+        `left` and `right` respectively. Pass a value of `None` instead
+        of a string to indicate that the column name from `left` or
+        `right` should be left as-is, with no prefix. At least one of the
+        values must not be None.
     copy : bool, default False
         If False, avoid copy if possible.
 

pandas/tests/reshape/merge/test_join.py

@@ -783,7 +783,7 @@ def test_join_dups(self):
         # GH 40991: As of 2.0 causes duplicate columns
         with pytest.raises(
             pd.errors.MergeError,
-            match="Passing 'suffixes' which cause duplicate columns",
+            match="Passing 'suffixes' or/and 'prefixes' which cause duplicate columns",
         ):
             dta.merge(w, left_index=True, right_index=True)
 

pandas/tests/reshape/merge/test_multi.py

@@ -652,7 +652,9 @@ def test_join_multi_levels_invalid(self, portfolio, household):
         portfolio2 = portfolio.copy()
         portfolio2.index.set_names(["household_id", "foo"])
 
-        with pytest.raises(ValueError, match="columns overlap but no suffix specified"):
+        with pytest.raises(
+            ValueError, match="columns overlap but no suffix or prefix specified"
+        ):
             portfolio2.join(portfolio, how="inner")
 
     def test_join_multi_levels2(self):