bpo-37408: Precise that Tarfile "format" argument only concerns writing. (GH-14389) (#16465)
(cherry picked from commit c5a7e0ce194c0eafe82eb3e431881012398e7d46)
Co-authored-by: Pascal Chambon <pythoniks@gmail.com>
diff --git a/Doc/library/tarfile.rst b/Doc/library/tarfile.rst
index f25af8c..c34f2c4 100644
--- a/Doc/library/tarfile.rst
+++ b/Doc/library/tarfile.rst
@@ -290,9 +290,10 @@
*fileobj* is not closed, when :class:`TarFile` is closed.
- *format* controls the archive format. It must be one of the constants
+ *format* controls the archive format for writing. It must be one of the constants
:const:`USTAR_FORMAT`, :const:`GNU_FORMAT` or :const:`PAX_FORMAT` that are
- defined at module level.
+ defined at module level. When reading, format will be automatically detected, even
+ if different formats are present in a single archive.
The *tarinfo* argument can be used to replace the default :class:`TarInfo` class
with a different one.