Mark Dickinson <dicki...@gmail.com> added the comment:
This isn't a bug. When you do `Decimal(9.95)`, you're converting the binary
floating-point number `9.95` to a `Decimal` instance. The conversion is
performed exactly, with no change in the value. But the *input* to the
conversion, the float `9.95` can't be stored exactly in IEEE 754 binary64
format, so what you end up with is something very slightly smaller.
>>> from decimal import Decimal
>>> Decimal(9.95)
Decimal('9.949999999999999289457264239899814128875732421875')
That's the reason that it rounds down.
Good practice is to create your Decimal instances from strings rather than
floats.
>>> Decimal(9.95).quantize(Decimal('1.1'),ROUND_HALF_UP)
Decimal('9.9')
>>> Decimal('9.95').quantize(Decimal('1.1'),ROUND_HALF_UP)
Decimal('10.0')
----------
nosy: +mark.dickinson
resolution: -> not a bug
stage: -> resolved
status: open -> closed
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue32908>
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