Issue27181 add geometric mean.

1 files changed, 285 insertions, 0 deletions

diff --git a/Lib/test/test_statistics.py b/Lib/test/test_statistics.py
index 4b3fd36..8b0c01f 100644
--- a/Lib/test/test_statistics.py
+++ b/Lib/test/test_statistics.py
@@ -1010,6 +1010,291 @@ class FailNegTest(unittest.TestCase):
         self.assertEqual(errmsg, msg)
 
 
+class Test_Product(NumericTestCase):
+    """Test the private _product function."""
+
+    def test_ints(self):
+        data = [1, 2, 5, 7, 9]
+        self.assertEqual(statistics._product(data), (0, 630))
+        self.assertEqual(statistics._product(data*100), (0, 630**100))
+
+    def test_floats(self):
+        data = [1.0, 2.0, 4.0, 8.0]
+        self.assertEqual(statistics._product(data), (8, 0.25))
+
+    def test_overflow(self):
+        # Test with floats that overflow.
+        data = [1e300]*5
+        self.assertEqual(statistics._product(data), (5980, 0.6928287951283193))
+
+    def test_fractions(self):
+        F = Fraction
+        data = [F(14, 23), F(69, 1), F(665, 529), F(299, 105), F(1683, 39)]
+        exp, mant = statistics._product(data)
+        self.assertEqual(exp, 0)
+        self.assertEqual(mant, F(2*3*7*11*17*19, 23))
+        self.assertTrue(isinstance(mant, F))
+        # Mixed Fraction and int.
+        data = [3, 25, F(2, 15)]
+        exp, mant = statistics._product(data)
+        self.assertEqual(exp, 0)
+        self.assertEqual(mant, F(10))
+        self.assertTrue(isinstance(mant, F))
+
+    @unittest.expectedFailure
+    def test_decimal(self):
+        D = Decimal
+        data = [D('24.5'), D('17.6'), D('0.025'), D('1.3')]
+        assert False
+
+    def test_mixed_decimal_float(self):
+        # Test that mixed Decimal and float raises.
+        self.assertRaises(TypeError, statistics._product, [1.0, Decimal(1)])
+        self.assertRaises(TypeError, statistics._product, [Decimal(1), 1.0])
+
+
+class Test_Nth_Root(NumericTestCase):
+    """Test the functionality of the private _nth_root function."""
+
+    def setUp(self):
+        self.nroot = statistics._nth_root
+
+    # --- Special values (infinities, NANs, zeroes) ---
+
+    def test_float_NAN(self):
+        # Test that the root of a float NAN is a float NAN.
+        NAN = float('nan')
+        for n in range(2, 9):
+            with self.subTest(n=n):
+                result = self.nroot(NAN, n)
+                self.assertTrue(math.isnan(result))
+
+    def test_decimal_QNAN(self):
+        # Test the  behaviour when taking the root of a Decimal quiet NAN.
+        NAN = decimal.Decimal('nan')
+        with decimal.localcontext() as ctx:
+            ctx.traps[decimal.InvalidOperation] = 1
+            self.assertRaises(decimal.InvalidOperation, self.nroot, NAN, 5)
+            ctx.traps[decimal.InvalidOperation] = 0
+            self.assertTrue(self.nroot(NAN, 5).is_qnan())
+
+    def test_decimal_SNAN(self):
+        # Test that taking the root of a Decimal sNAN always raises.
+        sNAN = decimal.Decimal('snan')
+        with decimal.localcontext() as ctx:
+            ctx.traps[decimal.InvalidOperation] = 1
+            self.assertRaises(decimal.InvalidOperation, self.nroot, sNAN, 5)
+            ctx.traps[decimal.InvalidOperation] = 0
+            self.assertRaises(decimal.InvalidOperation, self.nroot, sNAN, 5)
+
+    def test_inf(self):
+        # Test that the root of infinity is infinity.
+        for INF in (float('inf'), decimal.Decimal('inf')):
+            for n in range(2, 9):
+                with self.subTest(n=n, inf=INF):
+                    self.assertEqual(self.nroot(INF, n), INF)
+
+    def testNInf(self):
+        # Test that the root of -inf is -inf for odd n.
+        for NINF in (float('-inf'), decimal.Decimal('-inf')):
+            for n in range(3, 11, 2):
+                with self.subTest(n=n, inf=NINF):
+                    self.assertEqual(self.nroot(NINF, n), NINF)
+
+    # FIXME: need to check Decimal zeroes too.
+    def test_zero(self):
+        # Test that the root of +0.0 is +0.0.
+        for n in range(2, 11):
+            with self.subTest(n=n):
+                result = self.nroot(+0.0, n)
+                self.assertEqual(result, 0.0)
+                self.assertEqual(sign(result), +1)
+
+    # FIXME: need to check Decimal zeroes too.
+    def test_neg_zero(self):
+        # Test that the root of -0.0 is -0.0.
+        for n in range(2, 11):
+            with self.subTest(n=n):
+                result = self.nroot(-0.0, n)
+                self.assertEqual(result, 0.0)
+                self.assertEqual(sign(result), -1)
+
+    # --- Test return types ---
+
+    def check_result_type(self, x, n, outtype):
+        self.assertIsInstance(self.nroot(x, n), outtype)
+        class MySubclass(type(x)):
+            pass
+        self.assertIsInstance(self.nroot(MySubclass(x), n), outtype)
+
+    def testDecimal(self):
+        # Test that Decimal arguments return Decimal results.
+        self.check_result_type(decimal.Decimal('33.3'), 3, decimal.Decimal)
+
+    def testFloat(self):
+        # Test that other arguments return float results.
+        for x in (0.2, Fraction(11, 7), 91):
+            self.check_result_type(x, 6, float)
+
+    # --- Test bad input ---
+
+    def testBadOrderTypes(self):
+        # Test that nroot raises correctly when n has the wrong type.
+        for n in (5.0, 2j, None, 'x', b'x', [], {}, set(), sign):
+            with self.subTest(n=n):
+                self.assertRaises(TypeError, self.nroot, 2.5, n)
+
+    def testBadOrderValues(self):
+        # Test that nroot raises correctly when n has a wrong value.
+        for n in (1, 0, -1, -2, -87):
+            with self.subTest(n=n):
+                self.assertRaises(ValueError, self.nroot, 2.5, n)
+
+    def testBadTypes(self):
+        # Test that nroot raises correctly when x has the wrong type.
+        for x in (None, 'x', b'x', [], {}, set(), sign):
+            with self.subTest(x=x):
+                self.assertRaises(TypeError, self.nroot, x, 3)
+
+    def testNegativeEvenPower(self):
+        # Test negative x with even n raises correctly.
+        x = random.uniform(-20.0, -0.1)
+        assert x < 0
+        for n in range(2, 9, 2):
+            with self.subTest(x=x, n=n):
+                self.assertRaises(ValueError, self.nroot, x, n)
+
+    # --- Test that nroot is never worse than calling math.pow() ---
+
+    def check_error_is_no_worse(self, x, n):
+        y = math.pow(x, n)
+        with self.subTest(x=x, n=n, y=y):
+            err1 = abs(self.nroot(y, n) - x)
+            err2 = abs(math.pow(y, 1.0/n) - x)
+            self.assertLessEqual(err1, err2)
+
+    def testCompareWithPowSmall(self):
+        # Compare nroot with pow for small values of x.
+        for i in range(200):
+            x = random.uniform(1e-9, 1.0-1e-9)
+            n = random.choice(range(2, 16))
+            self.check_error_is_no_worse(x, n)
+
+    def testCompareWithPowMedium(self):
+        # Compare nroot with pow for medium-sized values of x.
+        for i in range(200):
+            x = random.uniform(1.0, 100.0)
+            n = random.choice(range(2, 16))
+            self.check_error_is_no_worse(x, n)
+
+    def testCompareWithPowLarge(self):
+        # Compare nroot with pow for largish values of x.
+        for i in range(200):
+            x = random.uniform(100.0, 10000.0)
+            n = random.choice(range(2, 16))
+            self.check_error_is_no_worse(x, n)
+
+    def testCompareWithPowHuge(self):
+        # Compare nroot with pow for huge values of x.
+        for i in range(200):
+            x = random.uniform(1e20, 1e50)
+            # We restrict the order here to avoid an Overflow error.
+            n = random.choice(range(2, 7))
+            self.check_error_is_no_worse(x, n)
+
+    # --- Test for numerically correct answers ---
+
+    def testExactPowers(self):
+        # Test that small integer powers are calculated exactly.
+        for i in range(1, 51):
+            for n in range(2, 16):
+                if (i, n) == (35, 13):
+                    # See testExpectedFailure35p13
+                    continue
+                with self.subTest(i=i, n=n):
+                    x = i**n
+                    self.assertEqual(self.nroot(x, n), i)
+
+    def testExactPowersNegatives(self):
+        # Test that small negative integer powers are calculated exactly.
+        for i in range(-1, -51, -1):
+            for n in range(3, 16, 2):
+                if (i, n) == (-35, 13):
+                    # See testExpectedFailure35p13
+                    continue
+                with self.subTest(i=i, n=n):
+                    x = i**n
+                    assert sign(x) == -1
+                    self.assertEqual(self.nroot(x, n), i)
+
+    def testExpectedFailure35p13(self):
+        # Test the expected failure 35**13 is almost exact.
+        x = 35**13
+        err = abs(self.nroot(x, 13) - 35)
+        self.assertLessEqual(err, 0.000000001)
+        err = abs(self.nroot(-x, 13) + 35)
+        self.assertLessEqual(err, 0.000000001)
+
+    def testOne(self):
+        # Test that the root of 1.0 is 1.0.
+        for n in range(2, 11):
+            with self.subTest(n=n):
+                self.assertEqual(self.nroot(1.0, n), 1.0)
+
+    def testFraction(self):
+        # Test Fraction results.
+        x = Fraction(89, 75)
+        self.assertEqual(self.nroot(x**12, 12), float(x))
+
+    def testInt(self):
+        # Test int results.
+        x = 276
+        self.assertEqual(self.nroot(x**24, 24), x)
+
+    def testBigInt(self):
+        # Test that ints too big to convert to floats work.
+        bignum = 10**20  # That's not that big...
+        self.assertEqual(self.nroot(bignum**280, 280), bignum)
+        # Can we make it bigger?
+        hugenum = bignum**50
+        # Make sure that it is too big to convert to a float.
+        try:
+            y = float(hugenum)
+        except OverflowError:
+            pass
+        else:
+            raise AssertionError('hugenum is not big enough')
+        self.assertEqual(self.nroot(hugenum, 50), float(bignum))
+
+    def testDecimal(self):
+        # Test Decimal results.
+        for s in '3.759 64.027 5234.338'.split():
+            x = decimal.Decimal(s)
+            with self.subTest(x=x):
+                a = self.nroot(x**5, 5)
+                self.assertEqual(a, x)
+                a = self.nroot(x**17, 17)
+                self.assertEqual(a, x)
+
+    def testFloat(self):
+        # Test float results.
+        for x in (3.04e-16, 18.25, 461.3, 1.9e17):
+            with self.subTest(x=x):
+                self.assertEqual(self.nroot(x**3, 3), x)
+                self.assertEqual(self.nroot(x**8, 8), x)
+                self.assertEqual(self.nroot(x**11, 11), x)
+
+
+class Test_NthRoot_NS(unittest.TestCase):
+    """Test internals of the nth_root function, hidden in _nroot_NS."""
+
+    def test_class_cannot_be_instantiated(self):
+        # Test that _nroot_NS cannot be instantiated.
+        # It should be a namespace, like in C++ or C#, but Python
+        # lacks that feature and so we have to make do with a class.
+        self.assertRaises(TypeError, statistics._nroot_NS)
+
+
 # === Tests for public functions ===
 
 class UnivariateCommonMixin: