gh-127805: Clarify Formatter initialization in logging.rst. (GH-127850)

diff --git a/Doc/library/logging.rst b/Doc/library/logging.rst
index 34bb46f0bb1ecb126731782949cd4dc6d752d944..72190e972405140495c726cdcf78fca3a92244b6 100644 (file)
--- a/Doc/library/logging.rst
+++ b/Doc/library/logging.rst
@@ -562,7 +562,8 @@ subclasses. However, the :meth:`!__init__` method in subclasses needs to call
 
    .. method:: Handler.setFormatter(fmt)
 
-      Sets the :class:`Formatter` for this handler to *fmt*.
+      Sets the formatter for this handler to *fmt*.
+      The *fmt* argument must be a :class:`Formatter` instance or ``None``.
 
 
    .. method:: Handler.addFilter(filter)