eachimei · Nov 11, 2026 · Nov 11, 2026
diff --git a/Doc/library/pickle.rst b/Doc/library/pickle.rst
@@ -296,10 +296,19 @@ The :mod:`!pickle` module exports three classes, :class:`Pickler`,
    If not specified, the default is :data:`DEFAULT_PROTOCOL`.  If a negative
    number is specified, :data:`HIGHEST_PROTOCOL` is selected.
 
-   The *file* argument must have a write() method that accepts a single bytes
-   argument.  It can thus be an on-disk file opened for binary writing, an
-   :class:`io.BytesIO` instance, or any other custom object that meets this
-   interface.
+   The *file* argument must have a write() method that accepts a single
+   :term:`bytes-like object` argument.  It can thus be an on-disk file opened
+   for binary writing, an :class:`io.BytesIO` instance, or any other custom
+   object that meets this interface.
+
+   .. note::
+
+      Depending on the protocol and on the objects being pickled, *write()*
+      may be passed :class:`bytes`, :class:`bytearray`, :class:`memoryview`
+      or :class:`PickleBuffer` instances.  Not all of these support
+      :func:`len`, and for a non-byte-format buffer :func:`len` does not give
+      the size in bytes; use ``memoryview(data).nbytes`` if the number of
+      bytes is needed.
 
    If *fix_imports* is true and *protocol* is less than 3, pickle will try to
    map the new Python 3 names to the old module names used in Python 2, so

diff --git a/Lib/pickle.py b/Lib/pickle.py
@@ -449,9 +449,9 @@ def __init__(self, file, protocol=None, *, fix_imports=True,
         produced.
 
         The *file* argument must have a write() method that accepts a
-        single bytes argument. It can thus be a file object opened for
-        binary writing, an io.BytesIO instance, or any other custom
-        object that meets this interface.
+        single bytes-like object argument. It can thus be a file object
+        opened for binary writing, an io.BytesIO instance, or any other
+        custom object that meets this interface.
 
         If *fix_imports* is True and *protocol* is less than 3, pickle
         will try to map the new Python 3 names to the old module names

diff --git a/Misc/NEWS.d/next/Documentation/2026-11-11-12-30-00.gh-issue-161803.H5Teu7.rst b/Misc/NEWS.d/next/Documentation/2026-11-11-12-30-00.gh-issue-161803.H5Teu7.rst
@@ -0,0 +1,3 @@
+Clarify that the *file* argument of :class:`pickle.Pickler` and
+:func:`pickle.dump` must have a ``write()`` method accepting a
+:term:`bytes-like object`, not only :class:`bytes`.
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
@@ -5298,9 +5298,9 @@ version supported.  The higher the protocol used, the more recent the
 version of Python needed to read the pickle produced.
 
 The *file* argument must have a write() method that accepts a single
-bytes argument. It can thus be a file object opened for binary
-writing, an io.BytesIO instance, or any other custom object that meets
-this interface.
+bytes-like object argument. It can thus be a file object opened for
+binary writing, an io.BytesIO instance, or any other custom object that
+meets this interface.
 
 If *fix_imports* is True and protocol is less than 3, pickle will try
 to map the new Python 3 names to the old module names used in Python
@@ -5323,7 +5323,7 @@ static int
 _pickle_Pickler___init___impl(PicklerObject *self, PyObject *file,
                               PyObject *protocol, int fix_imports,
                               PyObject *buffer_callback)
-/*[clinic end generated code: output=0abedc50590d259b input=cddc50f66b770002]*/
+/*[clinic end generated code: output=0abedc50590d259b input=fe16061a9f3ae4c3]*/
 {
     BEGIN_USING_PICKLER(self, -1);
     /* In case of multiple __init__() calls, clear previous content. */
@@ -8230,9 +8230,9 @@ version supported.  The higher the protocol used, the more recent the
 version of Python needed to read the pickle produced.
 
 The *file* argument must have a write() method that accepts a single
-bytes argument.  It can thus be a file object opened for binary
-writing, an io.BytesIO instance, or any other custom object that meets
-this interface.
+bytes-like object argument.  It can thus be a file object opened for
+binary writing, an io.BytesIO instance, or any other custom object that
+meets this interface.
 
 If *fix_imports* is True and protocol is less than 3, pickle will try
 to map the new Python 3 names to the old module names used in Python
@@ -8248,7 +8248,7 @@ static PyObject *
 _pickle_dump_impl(PyObject *module, PyObject *obj, PyObject *file,
                   PyObject *protocol, int fix_imports,
                   PyObject *buffer_callback)
-/*[clinic end generated code: output=706186dba996490c input=b89ce8d0e911fd46]*/
+/*[clinic end generated code: output=706186dba996490c input=3172ad2215ef9472]*/
 {
     PickleState *state = _Pickle_GetState(module);
     PicklerObject *pickler = _Pickler_New(state);

diff --git a/Modules/clinic/_pickle.c.h b/Modules/clinic/_pickle.c.h