bpo-37315: Deprecate accepting floats in math.factorial(). (GH-14147)
diff --git a/Doc/library/math.rst b/Doc/library/math.rst
index ff937d2..bfce41a 100644
--- a/Doc/library/math.rst
+++ b/Doc/library/math.rst
@@ -71,6 +71,9 @@
Return *x* factorial as an integer. Raises :exc:`ValueError` if *x* is not integral or
is negative.
+ .. deprecated:: 3.9
+ Accepting floats with integral values (like ``5.0``) is deprecated.
+
.. function:: floor(x)
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index 62b013f..c5cb626 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -109,6 +109,11 @@
Deprecated
==========
+* Currently :func:`math.factorial` accepts :class:`float` instances with
+ non-negative integer values (like ``5.0``). It raises a :exc:`ValueError`
+ for non-integral and negative floats. It is deprecated now. In future
+ Python versions it will raise a :exc:`TypeError` for all floats.
+ (Contributed by Serhiy Storchaka in :issue:`37315`.)
Removed
diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index adefa07..f259139 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -501,21 +501,25 @@
def testFactorial(self):
self.assertEqual(math.factorial(0), 1)
- self.assertEqual(math.factorial(0.0), 1)
total = 1
for i in range(1, 1000):
total *= i
self.assertEqual(math.factorial(i), total)
- self.assertEqual(math.factorial(float(i)), total)
self.assertEqual(math.factorial(i), py_factorial(i))
self.assertRaises(ValueError, math.factorial, -1)
- self.assertRaises(ValueError, math.factorial, -1.0)
self.assertRaises(ValueError, math.factorial, -10**100)
- self.assertRaises(ValueError, math.factorial, -1e100)
- self.assertRaises(ValueError, math.factorial, math.pi)
def testFactorialNonIntegers(self):
- self.assertRaises(TypeError, math.factorial, decimal.Decimal(5.2))
+ with self.assertWarns(DeprecationWarning):
+ self.assertEqual(math.factorial(5.0), 120)
+ with self.assertWarns(DeprecationWarning):
+ self.assertRaises(ValueError, math.factorial, 5.2)
+ with self.assertWarns(DeprecationWarning):
+ self.assertRaises(ValueError, math.factorial, -1.0)
+ with self.assertWarns(DeprecationWarning):
+ self.assertRaises(ValueError, math.factorial, -1e100)
+ self.assertRaises(TypeError, math.factorial, decimal.Decimal('5'))
+ self.assertRaises(TypeError, math.factorial, decimal.Decimal('5.2'))
self.assertRaises(TypeError, math.factorial, "5")
# Other implementations may place different upper bounds.
@@ -524,7 +528,8 @@
# Currently raises ValueError for inputs that are too large
# to fit into a C long.
self.assertRaises(OverflowError, math.factorial, 10**100)
- self.assertRaises(OverflowError, math.factorial, 1e100)
+ with self.assertWarns(DeprecationWarning):
+ self.assertRaises(OverflowError, math.factorial, 1e100)
def testFloor(self):
self.assertRaises(TypeError, math.floor)
diff --git a/Misc/NEWS.d/next/Library/2019-06-17-11-59-52.bpo-37315.o1xFC0.rst b/Misc/NEWS.d/next/Library/2019-06-17-11-59-52.bpo-37315.o1xFC0.rst
new file mode 100644
index 0000000..fd59819
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-06-17-11-59-52.bpo-37315.o1xFC0.rst
@@ -0,0 +1,2 @@
+Deprecated accepting floats with integral value (like ``5.0``) in
+:func:`math.factorial`.
diff --git a/Modules/mathmodule.c b/Modules/mathmodule.c
index 82a9a14..a75a3c9 100644
--- a/Modules/mathmodule.c
+++ b/Modules/mathmodule.c
@@ -1981,6 +1981,12 @@
PyObject *result, *odd_part, *pyint_form;
if (PyFloat_Check(arg)) {
+ if (PyErr_WarnEx(PyExc_DeprecationWarning,
+ "Using factorial() with floats is deprecated",
+ 1) < 0)
+ {
+ return NULL;
+ }
PyObject *lx;
double dx = PyFloat_AS_DOUBLE((PyFloatObject *)arg);
if (!(Py_IS_FINITE(dx) && dx == floor(dx))) {