Mar 25, 2026 · Mar 25, 2026
diff --git a/Doc/deprecations/pending-removal-in-3.20.rst b/Doc/deprecations/pending-removal-in-3.20.rst
  -:mod:`zlib`

  (Contributed by Hugo van Kemenade and Stan Ulbrych in:gh:`76007`.)

 * The ``__getformat__()`` class method of the:class:`float` is deprecated
  and will be removed in Python 3.20.

  (Contributed by Sergey B Kirpichev in:gh:`145633`.)
diff --git a/Lib/test/pythoninfo.py b/Lib/test/pythoninfo.py
 info_add('locale.getencoding',locale.getencoding())


 defcollect_builtins(info_add):
 info_add('builtins.float.float_format',float.__getformat__("float"))
 info_add('builtins.float.double_format',float.__getformat__("double"))


 defcollect_urandom(info_add):
 importos

 # its state.
 collect_urandom,

 collect_builtins,
 collect_cc,
 collect_curses,
 collect_datetime,
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
 # for a discussion of this number.
 SOCK_MAX_SIZE = 16 * 1024 * 1024 + 1

 def _have_ieee_doubles():
    import math
    # Check parameters for encoding of floats; a quick exit
    # if they aren't same as for IEC 60559 doubles.  Check
    # also that subnormals are present.
    if (ctypes.sizeof(ctypes.c_double) != 8
            or sys.float_info.radix != 2
            or sys.float_info.mant_dig != 53
            or sys.float_info.dig != 15
            or sys.float_info.min_exp != -1021
            or sys.float_info.min_10_exp != -307
            or sys.float_info.max_exp != 1024
            or sys.float_info.max_10_exp != 308
            or not math.issubnormal(math.nextafter(0, 1))):
        return False
    try:
        import ctypes
    except ImportError:
        return True
    # We attempt to determine if this machine is using IEC
    # floating-point formats by peering at the bits of some
    # carefully chosen value.  Assume that integer and
    # floating-point types have same endianness.
    d = 9006104071832581.0
    be_d = int.from_bytes(b"\x43\x3f\xff\x01\x02\x03\x04\x05")
    dp = ctypes.pointer(ctypes.c_double(d))
    lp = ctypes.cast(dp, ctypes.POINTER(ctypes.c_uint64))
    return lp[0] == be_d

 HAVE_IEEE_754 = _have_ieee_doubles()

 # decorator for skipping tests on non-IEEE 754 platforms
 requires_IEEE_754 = unittest.skipUnless(
 float.__getformat__("double").startswith("IEEE"),
 HAVE_IEEE_754,
    "test requires IEEE 754 doubles")

 def requires_zlib(reason='requires zlib'):
diff --git a/Lib/test/test_capi/test_float.py b/Lib/test/test_capi/test_float.py
 fromtest.test_capi.test_getargsimport (Float,FloatSubclass,FloatSubclass2,
 BadIndex2,BadFloat2,Index,BadIndex,
 BadFloat)
 fromtestimportsupport
 fromtest.supportimportimport_helper

 _testcapi=import_helper.import_module('_testcapi')
 8:2.0**-53,# binary64
 }

 HAVE_IEEE_754=float.__getformat__("double").startswith("IEEE")
 INF=float("inf")
 NAN=float("nan")

 self.assertEqual(unpack(b'\x00\x00\x00\x00\x00\x00\xf8?',LITTLE_ENDIAN),
 1.5)

 @support.requires_IEEE_754
 deftest_pack_unpack_roundtrip(self):
 pack=_testcapi.float_pack
 unpack=_testcapi.float_unpack

 large=2.0**100
 values= [1.0,1.5,large,1.0/7,math.pi]
 ifHAVE_IEEE_754:
 values.extend((INF,NAN))
 values= [1.0,1.5,large,1.0/7,math.pi,INF,NAN]
 forvalueinvalues:
 forsizein (2,4,8,):
 ifsize==2andvalue==large:
 else:
 self.assertEqual(value2,value)

 @unittest.skipUnless(HAVE_IEEE_754,"requires IEEE 754")
 @support.requires_IEEE_754
 deftest_pack_unpack_roundtrip_for_nans(self):
 pack=_testcapi.float_pack
 unpack=_testcapi.float_unpack
 self.assertTrue(math.isnan(value))
 self.assertEqual(data1,data2)

 @unittest.skipUnless(HAVE_IEEE_754,"requires IEEE 754")
 @support.requires_IEEE_754
 @unittest.skipUnless(sys.maxsize!=2147483647,"requires 64-bit mode")
 deftest_pack_unpack_nans_for_different_formats(self):
 pack=_testcapi.float_pack
diff --git a/Lib/test/test_float.py b/Lib/test/test_float.py
 self.assertFalse(f>=i)


 @unittest.skipUnless(hasattr(float,"__getformat__"),"requires __getformat__")
 classFormatFunctionsTestCase(unittest.TestCase):
 deftest_getformat(self):
 self.assertIn(float.__getformat__('double'),
                      ['unknown','IEEE, big-endian','IEEE, little-endian'])
 self.assertIn(float.__getformat__('float'),
                      ['unknown','IEEE, big-endian','IEEE, little-endian'])
 self.assertRaises(ValueError,float.__getformat__,'chicken')
 self.assertRaises(TypeError,float.__getformat__,1)


 BE_DOUBLE_INF=b'\x7f\xf0\x00\x00\x00\x00\x00\x00'
 LE_DOUBLE_INF=bytes(reversed(BE_DOUBLE_INF))
 BE_DOUBLE_NAN=b'\x7f\xf8\x00\x00\x00\x00\x00\x00'
diff --git a/Lib/test/test_funcattrs.py b/Lib/test/test_funcattrs.py

 # builtin classmethod:
 self.assertEqual(dict.fromkeys.__qualname__,'dict.fromkeys')
 self.assertEqual(float.__getformat__.__qualname__,
 'float.__getformat__')

 # builtin staticmethod:
 self.assertEqual(str.maketrans.__qualname__,'str.maketrans')

 # builtin classmethod:
 self.assertIs(dict.fromkeys.__self__,dict)
 self.assertIs(float.__getformat__.__self__,float)

 # builtin staticmethod:
 self.assertIsNone(str.maketrans.__self__)
diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-03-24-17-29-19.gh-issue-145633.RtktKR.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-03-24-17-29-19.gh-issue-145633.RtktKR.rst
 The ``__getformat__()`` class method of the:class:`float` is deprecated.
 Patch by Sergey B Kirpichev.
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
 float___getformat___impl(PyTypeObject*type,constchar*typestr)
 /*[clinic end generated code: output=2bfb987228cc9628 input=0ae1ba35d192f704]*/
 {
 if (PyErr_WarnFormat(PyExc_DeprecationWarning,1,
 "float.__getformat__() is deprecated"))
    {
 returnNULL;
    }
 if (strcmp(typestr,"double")!=0&&strcmp(typestr,"float")!=0) {
 PyErr_SetString(PyExc_ValueError,
 "__getformat__() argument 1 must be "
Original file line number	Diff line number	Diff line change
Expand Up		@@ -38,3 +38,8 @@ Pending removal in Python 3.20
		-:mod:`zlib`

		(Contributed by Hugo van Kemenade and Stan Ulbrych in:gh:`76007`.)

		* The ``__getformat__()`` class method of the:class:`float` is deprecated
		and will be removed in Python 3.20.

		(Contributed by Sergey B Kirpichev in:gh:`145633`.)
Original file line number	Diff line number	Diff line change
Expand Up		@@ -195,11 +195,6 @@ def collect_locale(info_add):
		info_add('locale.getencoding',locale.getencoding())


		defcollect_builtins(info_add):
		info_add('builtins.float.float_format',float.__getformat__("float"))
		info_add('builtins.float.double_format',float.__getformat__("double"))


		defcollect_urandom(info_add):
		importos

Expand DownExpand Up		@@ -1050,7 +1045,6 @@ def collect_info(info):
		# its state.
		collect_urandom,

		collect_builtins,
		collect_cc,
		collect_curses,
		collect_datetime,
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -518,9 +518,40 @@ def dec(args, *kwargs):
		# for a discussion of this number.
		SOCK_MAX_SIZE = 16 * 1024 * 1024 + 1

		def _have_ieee_doubles():
		import math
		# Check parameters for encoding of floats; a quick exit
		# if they aren't same as for IEC 60559 doubles. Check
		# also that subnormals are present.
		if (ctypes.sizeof(ctypes.c_double) != 8
		or sys.float_info.radix != 2
		or sys.float_info.mant_dig != 53
		or sys.float_info.dig != 15
		or sys.float_info.min_exp != -1021
		or sys.float_info.min_10_exp != -307
		or sys.float_info.max_exp != 1024
		or sys.float_info.max_10_exp != 308
		or not math.issubnormal(math.nextafter(0, 1))):
		return False
		try:
		import ctypes
		except ImportError:
		return True
		# We attempt to determine if this machine is using IEC
		# floating-point formats by peering at the bits of some
		# carefully chosen value. Assume that integer and
		# floating-point types have same endianness.
		d = 9006104071832581.0
		be_d = int.from_bytes(b"\x43\x3f\xff\x01\x02\x03\x04\x05")
		dp = ctypes.pointer(ctypes.c_double(d))
		lp = ctypes.cast(dp, ctypes.POINTER(ctypes.c_uint64))
		return lp[0] == be_d

		HAVE_IEEE_754 = _have_ieee_doubles()

		# decorator for skipping tests on non-IEEE 754 platforms
		requires_IEEE_754 = unittest.skipUnless(
		float.__getformat__("double").startswith("IEEE"),
		HAVE_IEEE_754,
		"test requires IEEE 754 doubles")

		def requires_zlib(reason='requires zlib'):
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -7,6 +7,7 @@
		fromtest.test_capi.test_getargsimport (Float,FloatSubclass,FloatSubclass2,
		BadIndex2,BadFloat2,Index,BadIndex,
		BadFloat)
		fromtestimportsupport
		fromtest.supportimportimport_helper

		_testcapi=import_helper.import_module('_testcapi')
Expand All		@@ -23,7 +24,6 @@
		8:2.0**-53,# binary64
		}

		HAVE_IEEE_754=float.__getformat__("double").startswith("IEEE")
		INF=float("inf")
		NAN=float("nan")

Expand DownExpand Up		@@ -170,14 +170,13 @@ def test_unpack(self):
		self.assertEqual(unpack(b'\x00\x00\x00\x00\x00\x00\xf8?',LITTLE_ENDIAN),
		1.5)

		@support.requires_IEEE_754
		deftest_pack_unpack_roundtrip(self):
		pack=_testcapi.float_pack
		unpack=_testcapi.float_unpack

		large=2.0**100
		values= [1.0,1.5,large,1.0/7,math.pi]
		ifHAVE_IEEE_754:
		values.extend((INF,NAN))
		values= [1.0,1.5,large,1.0/7,math.pi,INF,NAN]
		forvalueinvalues:
		forsizein (2,4,8,):
		ifsize==2andvalue==large:
Expand All		@@ -196,7 +195,7 @@ def test_pack_unpack_roundtrip(self):
		else:
		self.assertEqual(value2,value)

		@unittest.skipUnless(HAVE_IEEE_754,"requires IEEE 754")
		@support.requires_IEEE_754
		deftest_pack_unpack_roundtrip_for_nans(self):
		pack=_testcapi.float_pack
		unpack=_testcapi.float_unpack
Expand DownExpand Up		@@ -228,7 +227,7 @@ def test_pack_unpack_roundtrip_for_nans(self):
		self.assertTrue(math.isnan(value))
		self.assertEqual(data1,data2)

		@unittest.skipUnless(HAVE_IEEE_754,"requires IEEE 754")
		@support.requires_IEEE_754
		@unittest.skipUnless(sys.maxsize!=2147483647,"requires 64-bit mode")
		deftest_pack_unpack_nans_for_different_formats(self):
		pack=_testcapi.float_pack
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -670,17 +670,6 @@ def __neg__(self):
		self.assertFalse(f>=i)


		@unittest.skipUnless(hasattr(float,"__getformat__"),"requires __getformat__")
		classFormatFunctionsTestCase(unittest.TestCase):
		deftest_getformat(self):
		self.assertIn(float.__getformat__('double'),
		['unknown','IEEE, big-endian','IEEE, little-endian'])
		self.assertIn(float.__getformat__('float'),
		['unknown','IEEE, big-endian','IEEE, little-endian'])
		self.assertRaises(ValueError,float.__getformat__,'chicken')
		self.assertRaises(TypeError,float.__getformat__,1)


		BE_DOUBLE_INF=b'\x7f\xf0\x00\x00\x00\x00\x00\x00'
		LE_DOUBLE_INF=bytes(reversed(BE_DOUBLE_INF))
		BE_DOUBLE_NAN=b'\x7f\xf8\x00\x00\x00\x00\x00\x00'
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -486,8 +486,6 @@ def test_builtin__qualname__(self):

		# builtin classmethod:
		self.assertEqual(dict.fromkeys.__qualname__,'dict.fromkeys')
		self.assertEqual(float.__getformat__.__qualname__,
		'float.__getformat__')

		# builtin staticmethod:
		self.assertEqual(str.maketrans.__qualname__,'str.maketrans')
Expand All		@@ -509,7 +507,6 @@ def test_builtin__self__(self):

		# builtin classmethod:
		self.assertIs(dict.fromkeys.__self__,dict)
		self.assertIs(float.__getformat__.__self__,float)

		# builtin staticmethod:
		self.assertIsNone(str.maketrans.__self__)
Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		The ``__getformat__()`` class method of the:class:`float` is deprecated.
		Patch by Sergey B Kirpichev.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1696,6 +1696,11 @@ static PyObject *
		float___getformat___impl(PyTypeObjecttype,constchartypestr)
		/[clinic end generated code: output=2bfb987228cc9628 input=0ae1ba35d192f704]/
		{
		if (PyErr_WarnFormat(PyExc_DeprecationWarning,1,
		"float.__getformat__() is deprecated"))
		{
		returnNULL;
		}
		if (strcmp(typestr,"double")!=0&&strcmp(typestr,"float")!=0) {
		PyErr_SetString(PyExc_ValueError,
		"__getformat__() argument 1 must be "
Expand Down