Review (jreback)

pandas-dev · jreback · Jun 1, 2019 · Nov 29, 2018 · Nov 29, 2018 · Nov 30, 2018
commit c9c74966e90ce6745c3c9481163ed2404988629c
diff --git a/doc/source/user_guide/text.rst b/doc/source/user_guide/text.rst
@@ -70,6 +70,17 @@ and replacing any remaining white spaces with underscores:
     ``.str`` methods which operate on elements of type ``list`` are not available on such a
     ``Series``.
 
+.. _text.warn_types:
+
+.. warning::
+
+    Before v.0.25.0, the ``.str``-accessor did only the most rudimentary type checks. Starting with
+    v.0.25.0, the type of the Series is inferred (like it has already been the case for ``Index.str``),
+    and the allowed types (i.e. strings) are enforced more rigorously.
+
+    Generally speaking, the ``.str`` accessor is intended to work only on strings. With very few
+    exceptions, other uses are not supported, and may be disabled at a later point.
+
 
 Splitting and Replacing Strings
 -------------------------------

diff --git a/doc/source/whatsnew/v0.25.0.rst b/doc/source/whatsnew/v0.25.0.rst
@@ -172,6 +172,15 @@ Conversion
 Strings
 ^^^^^^^
 
+**The ``.str``-accessor performs stricter type checks**
+
+Due to the lack of a native string dtype in numpy, :attr:`Series.str` only checked whether the data was of ``object`` dtype.
+From now on, the inferred dtype of the Series is checked to be correct (particularly, not ``'bytes'``), as :attr:`Index.str` does already.
+
+For more details, see this :ref:`warning<text.warn_types>`.
+
+**Other bugs**
+
 - Bug in the ``__name__`` attribute of several methods of :class:`Series.str`, which were set incorrectly (:issue:`23551`)
 -
 -

diff --git a/pandas/core/strings.py b/pandas/core/strings.py
@@ -1764,7 +1764,7 @@ def forbid_nonstring_types(forbidden, name=None):
 
     Parameters
     ----------
-    forbidden : list or None
+    forbidden : list-of-str or None
         List of forbidden non-string types, may be one or more of
         `['bytes', 'mixed', 'mixed-integer']`.
     name : str, default None