DOC: rephrase CoW ChainedAssignmentError message now CoW is always enabled (#61970)

Author: jorisvandenbossche

pandas/errors/cow.py

@@ -1,24 +1,28 @@
 _chained_assignment_msg = (
     "A value is trying to be set on a copy of a DataFrame or Series "
     "through chained assignment.\n"
-    "When using the Copy-on-Write mode, such chained assignment never works "
-    "to update the original DataFrame or Series, because the intermediate "
-    "object on which we are setting values always behaves as a copy.\n\n"
+    "Such chained assignment never works to update the original DataFrame or "
+    "Series, because the intermediate object on which we are setting values "
+    "always behaves as a copy (due to Copy-on-Write).\n\n"
     "Try using '.loc[row_indexer, col_indexer] = value' instead, to perform "
     "the assignment in a single step.\n\n"
-    "See the caveats in the documentation: "
+    "See the documentation for a more detailed explanation: "
     "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
-    "copy_on_write.html"
+    "copy_on_write.html#chained-assignment"
 )
 
 
 _chained_assignment_method_msg = (
     "A value is trying to be set on a copy of a DataFrame or Series "
     "through chained assignment using an inplace method.\n"
-    "When using the Copy-on-Write mode, such inplace method never works "
-    "to update the original DataFrame or Series, because the intermediate "
-    "object on which we are setting values always behaves as a copy.\n\n"
+    "Such inplace method never works to update the original DataFrame or Series, "
+    "because the intermediate object on which we are setting values always "
+    "behaves as a copy (due to Copy-on-Write).\n\n"
     "For example, when doing 'df[col].method(value, inplace=True)', try "
     "using 'df.method({col: value}, inplace=True)' instead, to perform "
-    "the operation inplace on the original object.\n\n"
+    "the operation inplace on the original object, or try to avoid an inplace "
+    "operation using 'df[col] = df[col].method(value)'.\n\n"
+    "See the documentation for a more detailed explanation: "
+    "https://pandas.pydata.org/pandas-docs/stable/user_guide/"
+    "copy_on_write.html"
 )