mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-10-09 08:31:26 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 13

bpo-37128: Add math.perm(). (GH-13731)

Browse source
This commit is contained in:
Serhiy Storchaka 2019-06-02 11:16:49 +03:00 • committed by GitHub
parent d71f3170ac
commit 5ae299ac78
No known key found for this signature in database
GPG key ID: 4AEE18F83AFDEB23
5 changed files with 244 additions and 3 deletions
Download patch file Download diff file Expand all files Collapse all files

66
Lib/test/test_math.py
View file

@ -240,6 +240,9 @@ def result_check(expected, got, ulp_tol=5, abs_tol=0.0):
else:
return None
class IntSubclass(int):
pass
# Class providing an __index__ method.
class MyIndexable(object):
def __init__(self, value):
@ -1862,6 +1865,64 @@ class IsCloseTests(unittest.TestCase):
self.assertAllClose(fraction_examples, rel_tol=1e-8)
self.assertAllNotClose(fraction_examples, rel_tol=1e-9)
def testPerm(self):
perm = math.perm
factorial = math.factorial
# Test if factorial defintion is satisfied
for n in range(100):
for k in range(n + 1):
self.assertEqual(perm(n, k),
factorial(n) // factorial(n - k))
# Test for Pascal's identity
for n in range(1, 100):
for k in range(1, n):
self.assertEqual(perm(n, k), perm(n - 1, k - 1) * k + perm(n - 1, k))
# Test corner cases
for n in range(1, 100):
self.assertEqual(perm(n, 0), 1)
self.assertEqual(perm(n, 1), n)
self.assertEqual(perm(n, n), factorial(n))
# Raises TypeError if any argument is non-integer or argument count is
# not 2
self.assertRaises(TypeError, perm, 10, 1.0)
self.assertRaises(TypeError, perm, 10, decimal.Decimal(1.0))
self.assertRaises(TypeError, perm, 10, "1")
self.assertRaises(TypeError, perm, 10.0, 1)
self.assertRaises(TypeError, perm, decimal.Decimal(10.0), 1)
self.assertRaises(TypeError, perm, "10", 1)
self.assertRaises(TypeError, perm, 10)
self.assertRaises(TypeError, perm, 10, 1, 3)
self.assertRaises(TypeError, perm)
# Raises Value error if not k or n are negative numbers
self.assertRaises(ValueError, perm, -1, 1)
self.assertRaises(ValueError, perm, -2**1000, 1)
self.assertRaises(ValueError, perm, 1, -1)
self.assertRaises(ValueError, perm, 1, -2**1000)
# Raises value error if k is greater than n
self.assertRaises(ValueError, perm, 1, 2)
self.assertRaises(ValueError, perm, 1, 2**1000)
n = 2**1000
self.assertEqual(perm(n, 0), 1)
self.assertEqual(perm(n, 1), n)
self.assertEqual(perm(n, 2), n * (n-1))
self.assertRaises((OverflowError, MemoryError), perm, n, n)
for n, k in (True, True), (True, False), (False, False):
self.assertEqual(perm(n, k), 1)
self.assertIs(type(perm(n, k)), int)
self.assertEqual(perm(IntSubclass(5), IntSubclass(2)), 20)
self.assertEqual(perm(MyIndexable(5), MyIndexable(2)), 20)
for k in range(3):
self.assertIs(type(perm(IntSubclass(5), IntSubclass(k))), int)
self.assertIs(type(perm(MyIndexable(5), MyIndexable(k))), int)
def testComb(self):
comb = math.comb
factorial = math.factorial
@ -1925,8 +1986,11 @@ class IsCloseTests(unittest.TestCase):
for n, k in (True, True), (True, False), (False, False):
self.assertEqual(comb(n, k), 1)
self.assertIs(type(comb(n, k)), int)
self.assertEqual(comb(IntSubclass(5), IntSubclass(2)), 10)
self.assertEqual(comb(MyIndexable(5), MyIndexable(2)), 10)
self.assertIs(type(comb(MyIndexable(5), MyIndexable(2))), int)
for k in range(3):
self.assertIs(type(comb(IntSubclass(5), IntSubclass(k))), int)
self.assertIs(type(comb(MyIndexable(5), MyIndexable(k))), int)
def test_main():