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Issue #25928: Add Decimal.as_integer_ratio(). Python parts and docs by

Browse source 
Mark Dickinson.
This commit is contained in:
Stefan Krah 2015-12-28 23:02:02 +01:00
parent ac1e7f6983
commit 53f2e0ad45
7 changed files with 213 additions and 3 deletions
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33
Lib/test/test_decimal.py
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@ -2047,6 +2047,39 @@ class UsabilityTest(unittest.TestCase):
d = Decimal( (1, (0, 2, 7, 1), 'F') )
self.assertEqual(d.as_tuple(), (1, (0,), 'F'))
def test_as_integer_ratio(self):
Decimal = self.decimal.Decimal
# exceptional cases
self.assertRaises(OverflowError,
Decimal.as_integer_ratio, Decimal('inf'))
self.assertRaises(OverflowError,
Decimal.as_integer_ratio, Decimal('-inf'))
self.assertRaises(ValueError,
Decimal.as_integer_ratio, Decimal('-nan'))
self.assertRaises(ValueError,
Decimal.as_integer_ratio, Decimal('snan123'))
for exp in range(-4, 2):
for coeff in range(1000):
for sign in '+', '-':
d = Decimal('%s%dE%d' % (sign, coeff, exp))
pq = d.as_integer_ratio()
p, q = pq
# check return type
self.assertIsInstance(pq, tuple)
self.assertIsInstance(p, int)
self.assertIsInstance(q, int)
# check normalization: q should be positive;
# p should be relatively prime to q.
self.assertGreater(q, 0)
self.assertEqual(math.gcd(p, q), 1)
# check that p/q actually gives the correct value
self.assertEqual(Decimal(p) / Decimal(q), d)
def test_subclassing(self):
# Different behaviours when subclassing Decimal
Decimal = self.decimal.Decimal