bpo-45155 : Default arguments for int.to_bytes(length=1, byteorder=sys.byteorder)

Doc/library/stdtypes.rst

@@ -499,7 +499,7 @@ class`. In addition, it provides a few more methods:
 
     .. versionadded:: 3.10
 
-.. method:: int.to_bytes(length, byteorder, *, signed=False)
+.. method:: int.to_bytes(length=1, byteorder='big', *, signed=False)
 
     Return an array of bytes representing an integer.
 
@@ -513,25 +513,31 @@ class`. In addition, it provides a few more methods:
         >>> x.to_bytes((x.bit_length() + 7) // 8, byteorder='little')
         b'\xe8\x03'
 
-    The integer is represented using *length* bytes.  An :exc:`OverflowError`
-    is raised if the integer is not representable with the given number of
-    bytes.
+    The integer is represented using *length* bytes, and defaults to 1.  An
+    :exc:`OverflowError` is raised if the integer is not representable with
+    the given number of bytes.
 
     The *byteorder* argument determines the byte order used to represent the
-    integer.  If *byteorder* is ``"big"``, the most significant byte is at the
-    beginning of the byte array.  If *byteorder* is ``"little"``, the most
-    significant byte is at the end of the byte array.  To request the native
-    byte order of the host system, use :data:`sys.byteorder` as the byte order
-    value.
+    integer, and defaults to ``"big"``.  If *byteorder* is
+    ``"big"``, the most significant byte is at the beginning of the byte
+    array.  If *byteorder* is ``"little"``, the most significant byte is at
+    the end of the byte array.
 
     The *signed* argument determines whether two's complement is used to
     represent the integer.  If *signed* is ``False`` and a negative integer is
     given, an :exc:`OverflowError` is raised. The default value for *signed*
     is ``False``.
 
+    The default values can be used to conveniently turn an integer into a
+    single byte object.  However, when using the default arguments, don't try
+    to convert a value greater than 255 or you'll get an :exc:`OverflowError`::
+
+        >>> (65).to_bytes()
+        b'A'
+
     Equivalent to::
 
-        def to_bytes(n, length, byteorder, signed=False):
+        def to_bytes(n, length=1, byteorder='big', signed=False):
             if byteorder == 'little':
                 order = range(length)
             elif byteorder == 'big':
@@ -542,8 +548,10 @@ class`. In addition, it provides a few more methods:
             return bytes((n >> i*8) & 0xff for i in order)
 
     .. versionadded:: 3.2
+    .. versionchanged:: 3.11
+       Added default argument values for ``length`` and ``byteorder``.
 
-.. classmethod:: int.from_bytes(bytes, byteorder, *, signed=False)
+.. classmethod:: int.from_bytes(bytes, byteorder='big', *, signed=False)
 
     Return the integer represented by the given array of bytes.
 
@@ -562,18 +570,18 @@ class`. In addition, it provides a few more methods:
     iterable producing bytes.
 
     The *byteorder* argument determines the byte order used to represent the
-    integer.  If *byteorder* is ``"big"``, the most significant byte is at the
-    beginning of the byte array.  If *byteorder* is ``"little"``, the most
-    significant byte is at the end of the byte array.  To request the native
-    byte order of the host system, use :data:`sys.byteorder` as the byte order
-    value.
+    integer, and defaults to ``"big"``.  If *byteorder* is
+    ``"big"``, the most significant byte is at the beginning of the byte
+    array.  If *byteorder* is ``"little"``, the most significant byte is at
+    the end of the byte array.  To request the native byte order of the host
+    system, use :data:`sys.byteorder` as the byte order value.
 
     The *signed* argument indicates whether two's complement is used to
     represent the integer.
 
     Equivalent to::
 
-        def from_bytes(bytes, byteorder, signed=False):
+        def from_bytes(bytes, byteorder='big', signed=False):
             if byteorder == 'little':
                 little_ordered = list(bytes)
             elif byteorder == 'big':
@@ -588,6 +596,8 @@ class`. In addition, it provides a few more methods:
             return n
 
     .. versionadded:: 3.2
+    .. versionchanged:: 3.11
+       Added default argument value for ``byteorder``.
 
 .. method:: int.as_integer_ratio()
 

Lib/test/test_call.py

@@ -39,7 +39,7 @@ def test_varargs2(self):
         self.assertRaisesRegex(TypeError, msg, {}.__contains__, 0, 1)
 
     def test_varargs3(self):
-        msg = r"^from_bytes\(\) takes exactly 2 positional arguments \(3 given\)"
+        msg = r"^from_bytes\(\) takes at most 2 positional arguments \(3 given\)"
         self.assertRaisesRegex(TypeError, msg, int.from_bytes, b'a', 'little', False)
 
     def test_varargs1min(self):

Lib/test/test_long.py

@@ -1117,9 +1117,18 @@ def equivalent_python(n, length, byteorder, signed=False):
                         expected)
                 except Exception as err:
                     raise AssertionError(
-                        "failed to convert {0} with byteorder={1} and signed={2}"
+                        "failed to convert {} with byteorder={} and signed={}"
                         .format(test, byteorder, signed)) from err
 
+                # Test for all default arguments.
+                if len(expected) == 1 and byteorder == 'big' and not signed:
+                    try:
+                        self.assertEqual(test.to_bytes(), expected)
+                    except Exception as err:
+                        raise AssertionError(
+                            "failed to convert {} with default arguments"
+                            .format(test)) from err
+
                 try:
                     self.assertEqual(
                         equivalent_python(
@@ -1240,9 +1249,20 @@ def equivalent_python(byte_array, byteorder, signed=False):
                         expected)
                 except Exception as err:
                     raise AssertionError(
-                        "failed to convert {0} with byteorder={1!r} and signed={2}"
+                        "failed to convert {} with byteorder={!r} and signed={}"
                         .format(test, byteorder, signed)) from err
 
+                # Test for all default arguments.
+                if byteorder == 'big' and not signed:
+                    try:
+                        self.assertEqual(
+                            int.from_bytes(test),
+                            expected)
+                    except Exception as err:
+                        raise AssertionError(
+                            "failed to convert {} with default arugments"
+                            .format(test)) from err
+
                 try:
                     self.assertEqual(
                         equivalent_python(test, byteorder, signed=signed),

Misc/NEWS.d/next/Core and Builtins/2021-09-09-15-05-17.bpo-45155.JRw9TG.rst

@@ -0,0 +1,3 @@
+:meth:`int.to_bytes` and :meth:`int.from_bytes` now take a default value of
+``"big"`` for the ``byteorder`` argument.  :meth:`int.to_bytes` also takes a
+default value of ``1`` for the ``length`` argument.

Objects/longobject.c

@@ -5521,15 +5521,16 @@ int_as_integer_ratio_impl(PyObject *self)
 /*[clinic input]
 int.to_bytes
 
-    length: Py_ssize_t
+    length: Py_ssize_t = 1
         Length of bytes object to use.  An OverflowError is raised if the
-        integer is not representable with the given number of bytes.
-    byteorder: unicode
+        integer is not representable with the given number of bytes.  Default
+        is length 1.
+    byteorder: unicode(c_default="NULL") = "big"
         The byte order used to represent the integer.  If byteorder is 'big',
         the most significant byte is at the beginning of the byte array.  If
         byteorder is 'little', the most significant byte is at the end of the
         byte array.  To request the native byte order of the host system, use
-        `sys.byteorder' as the byte order value.
+        `sys.byteorder' as the byte order value.  Default is to use 'big'.
     *
     signed as is_signed: bool = False
         Determines whether two's complement is used to represent the integer.
@@ -5542,12 +5543,14 @@ Return an array of bytes representing an integer.
 static PyObject *
 int_to_bytes_impl(PyObject *self, Py_ssize_t length, PyObject *byteorder,
                   int is_signed)
-/*[clinic end generated code: output=89c801df114050a3 input=ddac63f4c7bf414c]*/
+/*[clinic end generated code: output=89c801df114050a3 input=d42ecfb545039d71]*/
 {
     int little_endian;
     PyObject *bytes;
 
-    if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_little))
+    if (byteorder == NULL)
+        little_endian = 0;
+    else if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_little))
         little_endian = 1;
     else if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_big))
         little_endian = 0;
@@ -5586,12 +5589,12 @@ int.from_bytes
         support the buffer protocol or be an iterable object producing bytes.
         Bytes and bytearray are examples of built-in objects that support the
         buffer protocol.
-    byteorder: unicode
+    byteorder: unicode(c_default="NULL") = "big"
         The byte order used to represent the integer.  If byteorder is 'big',
         the most significant byte is at the beginning of the byte array.  If
         byteorder is 'little', the most significant byte is at the end of the
         byte array.  To request the native byte order of the host system, use
-        `sys.byteorder' as the byte order value.
+        `sys.byteorder' as the byte order value.  Default is to use 'big'.
     *
     signed as is_signed: bool = False
         Indicates whether two's complement is used to represent the integer.
@@ -5602,12 +5605,14 @@ Return the integer represented by the given array of bytes.
 static PyObject *
 int_from_bytes_impl(PyTypeObject *type, PyObject *bytes_obj,
                     PyObject *byteorder, int is_signed)
-/*[clinic end generated code: output=efc5d68e31f9314f input=cdf98332b6a821b0]*/
+/*[clinic end generated code: output=efc5d68e31f9314f input=33326dccdd655553]*/
 {
     int little_endian;
     PyObject *long_obj, *bytes;
 
-    if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_little))
+    if (byteorder == NULL)
+        little_endian = 0;
+    else if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_little))
         little_endian = 1;
     else if (_PyUnicode_EqualToASCIIId(byteorder, &PyId_big))
         little_endian = 0;