gh-124130: Notes on empty string corner case of category \B (#124133)

y5c4l3 · picnixz · web-flow · commit d3e79d75d164 · 2024-09-23T08:58:14.000+02:00
Signed-off-by: y5c4l3 &lt;y5c4l3@proton.me&gt;
Co-authored-by: Bénédikt Tran &lt;10796600+picnixz@users.noreply.github.com&gt;
diff --git a/Doc/library/re.rst b/Doc/library/re.rst
@@ -572,6 +572,12 @@ character ``'$'``.
    Word boundaries are determined by the current locale
    if the :py:const:`~re.LOCALE` flag is used.
 
+   .. note::
+
+      Note that ``\B`` does not match an empty string, which differs from
+      RE implementations in other programming languages such as Perl.
+      This behavior is kept for compatibility reasons.
+
 .. index:: single: \d; in regular expressions
 
 ``\d``
