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bpo-37315: Deprecate accepting floats in math.factorial(). #14147

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serhiy-storchaka merged 2 commits into from
Jun 17, 2019
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bpo-37315: Deprecate accepting floats in math.factorial(). #14147

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bpo-37315: Deprecate accepting floats in math.factorial().
serhiy-storchaka Jun 17, 2019
ca162d5
Update Doc/whatsnew/3.9.rst
serhiy-storchaka Jun 17, 2019
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3 changes: 3 additions & 0 deletions Doc/library/math.rst
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Expand Up @@ -71,6 +71,9 @@ Number-theoretic and representation functions
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)

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5 changes: 5 additions & 0 deletions Doc/whatsnew/3.9.rst
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Expand Up @@ -107,6 +107,11 @@ Build and C API Changes
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
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19 changes: 12 additions & 7 deletions Lib/test/test_math.py
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Expand Up @@ -501,21 +501,25 @@ def testFabs(self):

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.
Expand All @@ -524,7 +528,8 @@ def testFactorialHugeInputs(self):
# 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)
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2019-06-17-11-59-52.bpo-37315.o1xFC0.rst
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@@ -0,0 +1,2 @@
Deprecated accepting floats with integral value (like ``5.0``) in
:func:`math.factorial`.
6 changes: 6 additions & 0 deletions Modules/mathmodule.c
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Expand Up @@ -1981,6 +1981,12 @@ math_factorial(PyObject *module, PyObject *arg)
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))) {
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