Merlijn van Deen added the comment:
As Zachary explained, the behavior is correct. There are three issues in play
here.
1) The rounding method. With the ROUND_HALF_EVEN rounding mode, .5 is rounded
to the nearest *even* number, so 1.65 is rounded to 1.6, while 1.75 is rounded
to 1.8.
2) Rounding of floats. Floats cannot represent every number, and numbers are
therefore rounded.
- round(2.675, 2) = round(2.6749999999999998, 2) and is thus rounded to 2.67
- round(1.65, 1) = round(1.6499999999999999, 1) and is thus rounded to 1.6
3a) In Python 2, round returns a float, so Decimal(round(Decimal("1.65"))) =
Decimal(1.6) =
Decimal('1.600000000000000088817841970012523233890533447265625') !=
Decimal('1.6')
3b) In Python 3, Decimal.__round__ is implemented, so round(D("1.65"), 1) ==
D("1.6") as expected.
----------
nosy: +valhallasw
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<http://bugs.python.org/issue24827>
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