Clarify acceptable values for BZ2File.__init__'s mode argument.
diff --git a/Doc/library/bz2.rst b/Doc/library/bz2.rst
index de5c825..893bb9b 100644
--- a/Doc/library/bz2.rst
+++ b/Doc/library/bz2.rst
@@ -35,9 +35,11 @@
be used to read or write the compressed data.
The *mode* argument can be either ``'r'`` for reading (default), ``'w'`` for
- overwriting, or ``'a'`` for appending. If *filename* is a file object (rather
- than an actual file name), a mode of ``'w'`` does not truncate the file, and
- is instead equivalent to ``'a'``.
+ overwriting, or ``'a'`` for appending. These can equivalently be given as
+ ``'rb'``, ``'wb'``, and ``'ab'`` respectively.
+
+ If *filename* is a file object (rather than an actual file name), a mode of
+ ``'w'`` does not truncate the file, and is instead equivalent to ``'a'``.
The *buffering* argument is ignored. Its use is deprecated.