DOC: Updated convert_dtype of Series.apply (pandas-dev#39941)

* DOC: Updated convert_dtype of Series.apply

* DOC: Updated convert_dtype for pandas.Series.apply

* DOC: Updated convert_dtype for pandas.Series.apply

* Editing the doc

* only mention categorical as example

* updates

Co-authored-by: Marco Gorelli <[email protected]>

Author: 2 people

pandas/core/series.py

@@ -4171,7 +4171,8 @@ def apply(
             Python function or NumPy ufunc to apply.
         convert_dtype : bool, default True
             Try to find better dtype for elementwise function results. If
-            False, leave as dtype=object.
+            False, leave as dtype=object. Note that the dtype is always
+            preserved for extension array dtypes, such as Categorical.
         args : tuple
             Positional arguments passed to func after the series value.
         **kwargs