Feb 5, 2025 · Feb 1, 2025 · Feb 1, 2025 · Feb 1, 2025 · Feb 2, 2025 · Feb 2, 2025
diff --git a/Doc/c-api/bytearray.rst b/Doc/c-api/bytearray.rst

 .. c:function:: int PyByteArray_Resize(PyObject *bytearray, Py_ssize_t len)

   Resize the internal buffer of *bytearray* to *len*.
   Resize the internal buffer of *bytearray* to *len*. Failure is a ``-1`` return with an exception set.

   .. versionchanged:: next
      A negative *len* will now result in a failure.


 Macros
 ^^^^^^
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
         optional *sep* and *bytes_per_sep* parameters to insert separators
         between bytes in the hex output.

   .. method:: resize(size)

      Resize the :class:`bytearray` to contain *size* bytes.
      If :class:`bytearray` needs to grow, all new bytes will be set to null bytes.

      .. versionadded:: next

 Since bytearray objects are sequences of integers (akin to a list), for a
 bytearray object *b*, ``b[0]`` will be an integer, while ``b[0:1]`` will be
 a bytearray object of length 1.  (This contrasts with text strings, where
diff --git a/Lib/test/test_bytes.py b/Lib/test/test_bytes.py
        b = by("Hello, world")
        self.assertEqual(re.findall(br"\w+", b), [by("Hello"), by("world")])

    def test_resize(self):
        ba = bytearray(b'abcdef')
        self.assertIsNone(ba.resize(3))
        self.assertEqual(ba, bytearray(b'abc'))
        self.assertIsNone(ba.resize(10))
        self.assertEqual(len(ba), 10)
        # Bytes beyond set values must be cleared.
        self.assertEqual(ba, bytearray(b'abc\0\0\0\0\0\0\0'))
        ba[3:10] = b'defghij'
        self.assertEqual(ba, bytearray(b'abcdefghij'))
        self.assertIsNone(ba.resize(2**20))
        self.assertEqual(len(ba), 2**20)
        self.assertEqual(ba, bytearray(b'abcdefghij' + b'\0' * (2 ** 20 - 10)))
        self.assertIsNone(ba.resize(0))
        self.assertEqual(ba, bytearray())
        self.assertIsNone(ba.resize(10))
        self.assertEqual(ba, bytearray(b'\0' * 10))

        ba = ByteArraySubclass(b'abcdef')
        self.assertIsNone(ba.resize(3))
        self.assertEqual(ba, bytearray(b'abc'))

        # Check arguments
        self.assertRaises(TypeError, lambda: bytearray().resize())
        self.assertRaises(TypeError, bytearray().resize, 10, 10)

        self.assertRaises(BufferError, lambda: bytearray().resize(-1))
        self.assertRaises(BufferError, lambda: bytearray().resize(-200))
        self.assertRaises(MemoryError, lambda: bytearray().resize(sys.maxsize))
        self.assertRaises(MemoryError, lambda: bytearray(1000).resize(sys.maxsize))


    def test_setitem(self):
        def setitem_as_mapping(b, i, val):
            b[i] = val
diff --git a/Lib/test/test_capi/test_bytearray.py b/Lib/test/test_capi/test_bytearray.py
        self.assertEqual(resize(ba, 3), 0)
        self.assertEqual(ba, bytearray(b'abc'))

        self.assertRaises(BufferError, resize, bytearray(), -1)
        self.assertRaises(BufferError, resize, bytearray(), -200)
        self.assertRaises(MemoryError, resize, bytearray(), PY_SSIZE_T_MAX)
        self.assertRaises(MemoryError, resize, bytearray(1000), PY_SSIZE_T_MAX)

        # CRASHES resize(bytearray(b'abc'), -1)
        # CRASHES resize(b'abc', 0)
        # CRASHES resize(object(), 0)
        # CRASHES resize(NULL, 0)
diff --git a/Misc/NEWS.d/next/Library/2025-02-01-14-55-33.gh-issue-129559.hQCeAz.rst b/Misc/NEWS.d/next/Library/2025-02-01-14-55-33.gh-issue-129559.hQCeAz.rst
 Add:meth:`bytearray.resize` method to:class:`bytearray` wrapping
 :c:func:`PyByteArray_Resize` so:class:`bytearray` can be efficiently
 resized in place.
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
    assert(self != NULL);
    assert(PyByteArray_Check(self));
    assert(logical_offset <= alloc);
    assert(requested_size >= 0);

    if (requested_size < 0) {
        PyErr_Format(PyExc_ValueError,
            "Can only resize to positive sizes, got %zd", requested_size);
        return -1;
    }

    if (requested_size == Py_SIZE(self)) {
        return 0;
 }


 /*[clinic input]
 bytearray.resize
    size: Py_ssize_t
        New size to resize to..
    /
 Resize the internal buffer of bytearray to len.
 [clinic start generated code]*/

 static PyObject *
 bytearray_resize_impl(PyByteArrayObject *self, Py_ssize_t size)
 /*[clinic end generated code: output=f73524922990b2d9 input=75fd4d17c4aa47d3]*/
 {
    Py_ssize_t start_size = PyByteArray_GET_SIZE(self);
    int result = PyByteArray_Resize((PyObject *)self, size);
    if (result < 0) {
        return NULL;
    }
    // Set new bytes to provide consistent / safer behavior in Python version.
    if (size > start_size) {
        memset(PyByteArray_AS_STRING(self) + start_size, 0, size - start_size);
    }
    Py_RETURN_NONE;
 }


 /*[clinic input]
 bytearray.translate

    BYTEARRAY_REPLACE_METHODDEF
    BYTEARRAY_REMOVEPREFIX_METHODDEF
    BYTEARRAY_REMOVESUFFIX_METHODDEF
    BYTEARRAY_RESIZE_METHODDEF
    BYTEARRAY_REVERSE_METHODDEF
    BYTEARRAY_RFIND_METHODDEF
    BYTEARRAY_RINDEX_METHODDEF
diff --git a/Objects/clinic/bytearrayobject.c.h b/Objects/clinic/bytearrayobject.c.h
Original file line number	Diff line number	Diff line change
Expand Up		@@ -73,7 +73,11 @@ Direct API functions

		.. c:function:: int PyByteArray_Resize(PyObject *bytearray, Py_ssize_t len)

		Resize the internal buffer of bytearray to len.
		Resize the internal buffer of bytearray to len. Failure is a ``-1`` return with an exception set.
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		.. versionchanged:: next
		A negative len will now result in a failure.
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		Macros
		^^^^^^
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2841,6 +2841,13 @@ objects.
		optional sep and bytes_per_sep parameters to insert separators
		between bytes in the hex output.

		.. method:: resize(size)

		Resize the :class:`bytearray` to contain size bytes.
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		If :class:`bytearray` needs to grow, all new bytes will be set to null bytes.
Copy link Member gpsheadFeb 5, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. Also describe the "obvious-to-us" behavior of what happens when it shrinks: the data at the end is truncated, the remaining data should be equivalent to a`[:size]` slice. ... and consider if the Python version should also support negative size to mean the same thing it would in a slice notation. `if (size < 0): size = max(0, len(self) + size)` ? Copy link ContributorAuthor cmaloneyFeb 5, 2025• edited Loading Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. 👍 for the truncation. I don't like negative, because the function operates in absolute buffer size, and requesting a negative buffer size sounds like a bug I'd write and I'd prefer an exception / exit rather than debug the symptom "my buffer shrank". Copy link ContributorAuthor cmaloneyFeb 5, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. my original equivalent to is wrong, which make it look like a delta, current doc one I'm validating: iflen(self)>size:delself[size:]else:self+=b'\0'* (size-len(self))

		.. versionadded:: next

		Since bytearray objects are sequences of integers (akin to a list), for a
		bytearray object b, ``b[0]`` will be an integer, while ``b[0:1]`` will be
		a bytearray object of length 1. (This contrasts with text strings, where
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1359,6 +1359,38 @@ def by(s):
		b = by("Hello, world")
		self.assertEqual(re.findall(br"\w+", b), [by("Hello"), by("world")])

		def test_resize(self):
		ba = bytearray(b'abcdef')
		self.assertIsNone(ba.resize(3))
		self.assertEqual(ba, bytearray(b'abc'))
		self.assertIsNone(ba.resize(10))
		self.assertEqual(len(ba), 10)
		# Bytes beyond set values must be cleared.
		self.assertEqual(ba, bytearray(b'abc\0\0\0\0\0\0\0'))
		ba[3:10] = b'defghij'
		self.assertEqual(ba, bytearray(b'abcdefghij'))
		self.assertIsNone(ba.resize(2**20))
		self.assertEqual(len(ba), 2**20)
		self.assertEqual(ba, bytearray(b'abcdefghij' + b'\0' * (2 ** 20 - 10)))
		self.assertIsNone(ba.resize(0))
		self.assertEqual(ba, bytearray())
		self.assertIsNone(ba.resize(10))
		self.assertEqual(ba, bytearray(b'\0' * 10))

		ba = ByteArraySubclass(b'abcdef')
		self.assertIsNone(ba.resize(3))
		self.assertEqual(ba, bytearray(b'abc'))
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		# Check arguments
		self.assertRaises(TypeError, lambda: bytearray().resize())
		self.assertRaises(TypeError, bytearray().resize, 10, 10)

		self.assertRaises(BufferError, lambda: bytearray().resize(-1))
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		self.assertRaises(BufferError, lambda: bytearray().resize(-200))
		self.assertRaises(MemoryError, lambda: bytearray().resize(sys.maxsize))
		self.assertRaises(MemoryError, lambda: bytearray(1000).resize(sys.maxsize))


		def test_setitem(self):
		def setitem_as_mapping(b, i, val):
		b[i] = val
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -151,10 +151,11 @@ def test_resize(self):
		self.assertEqual(resize(ba, 3), 0)
		self.assertEqual(ba, bytearray(b'abc'))

		self.assertRaises(BufferError, resize, bytearray(), -1)
		self.assertRaises(BufferError, resize, bytearray(), -200)
		self.assertRaises(MemoryError, resize, bytearray(), PY_SSIZE_T_MAX)
		self.assertRaises(MemoryError, resize, bytearray(1000), PY_SSIZE_T_MAX)

		# CRASHES resize(bytearray(b'abc'), -1)
		# CRASHES resize(b'abc', 0)
		# CRASHES resize(object(), 0)
		# CRASHES resize(NULL, 0)
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,3 @@
		Add:meth:`bytearray.resize` method to:class:`bytearray` wrapping
		:c:func:`PyByteArray_Resize` so:class:`bytearray` can be efficiently
		resized in place.
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Original file line number	Diff line number	Diff line change
Expand Up		@@ -184,7 +184,12 @@ PyByteArray_Resize(PyObject *self, Py_ssize_t requested_size)
		assert(self != NULL);
		assert(PyByteArray_Check(self));
		assert(logical_offset <= alloc);
		assert(requested_size >= 0);

		if (requested_size < 0) {
		PyErr_Format(PyExc_ValueError,
		"Can only resize to positive sizes, got %zd", requested_size);
		return -1;
		}

		if (requested_size == Py_SIZE(self)) {
		return 0;
Expand DownExpand Up		@@ -1388,6 +1393,31 @@ bytearray_removesuffix_impl(PyByteArrayObject self, Py_buffer suffix)
		}


		/*[clinic input]
		bytearray.resize
		size: Py_ssize_t
		New size to resize to..
		/
		Resize the internal buffer of bytearray to len.
		[clinic start generated code]*/

		static PyObject *
		bytearray_resize_impl(PyByteArrayObject *self, Py_ssize_t size)
		/[clinic end generated code: output=f73524922990b2d9 input=75fd4d17c4aa47d3]/
		{
		Py_ssize_t start_size = PyByteArray_GET_SIZE(self);
		int result = PyByteArray_Resize((PyObject *)self, size);
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		if (result < 0) {
		return NULL;
		}
		// Set new bytes to provide consistent / safer behavior in Python version.
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		if (size > start_size) {
		memset(PyByteArray_AS_STRING(self) + start_size, 0, size - start_size);
		}
		Py_RETURN_NONE;
		}


		/*[clinic input]
		bytearray.translate

Expand DownExpand Up		@@ -2361,6 +2391,7 @@ static PyMethodDef bytearray_methods[] = {
		BYTEARRAY_REPLACE_METHODDEF
		BYTEARRAY_REMOVEPREFIX_METHODDEF
		BYTEARRAY_REMOVESUFFIX_METHODDEF
		BYTEARRAY_RESIZE_METHODDEF
		BYTEARRAY_REVERSE_METHODDEF
		BYTEARRAY_RFIND_METHODDEF
		BYTEARRAY_RINDEX_METHODDEF
Expand Down