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Issue 4796: Add from_float methods to the decimal module.

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This commit is contained in:
Raymond Hettinger 2009-01-03 19:20:32 +00:00
parent 5f81741106
commit 771ed76102
4 changed files with 145 additions and 2 deletions
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49
Lib/test/test_decimal.py
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@ -1421,6 +1421,55 @@ class DecimalPythonAPItests(unittest.TestCase):
r = d.to_integral(ROUND_DOWN)
self.assertEqual(Decimal(math.trunc(d)), r)
def test_from_float(self):
class MyDecimal(Decimal):
pass
r = MyDecimal.from_float(0.1)
self.assertEqual(type(r), MyDecimal)
self.assertEqual(str(r),
'0.1000000000000000055511151231257827021181583404541015625')
bigint = 12345678901234567890123456789
self.assertEqual(MyDecimal.from_float(bigint), MyDecimal(bigint))
self.assert_(MyDecimal.from_float(float('nan')).is_qnan())
self.assert_(MyDecimal.from_float(float('inf')).is_infinite())
self.assert_(MyDecimal.from_float(float('-inf')).is_infinite())
self.assertEqual(str(MyDecimal.from_float(float('nan'))),
str(Decimal('NaN')))
self.assertEqual(str(MyDecimal.from_float(float('inf'))),
str(Decimal('Infinity')))
self.assertEqual(str(MyDecimal.from_float(float('-inf'))),
str(Decimal('-Infinity')))
self.assertRaises(TypeError, MyDecimal.from_float, 'abc')
for i in range(200):
x = random.expovariate(0.01) * (random.random() * 2.0 - 1.0)
self.assertEqual(x, float(MyDecimal.from_float(x))) # roundtrip
def test_create_decimal_from_float(self):
context = Context(prec=5, rounding=ROUND_DOWN)
self.assertEqual(
context.create_decimal_from_float(math.pi),
Decimal('3.1415')
)
context = Context(prec=5, rounding=ROUND_UP)
self.assertEqual(
context.create_decimal_from_float(math.pi),
Decimal('3.1416')
)
context = Context(prec=5, traps=[Inexact])
self.assertRaises(
Inexact,
context.create_decimal_from_float,
math.pi
)
self.assertEqual(repr(context.create_decimal_from_float(-0.0)),
"Decimal('-0')")
self.assertEqual(repr(context.create_decimal_from_float(1.0)),
"Decimal('1')")
self.assertEqual(repr(context.create_decimal_from_float(10)),
"Decimal('10')")
class ContextAPItests(unittest.TestCase):
def test_pickle(self):