Tim Peters added the comment:
Thanks, Mark! I didn't even know __round__ had become a dunder method.
For the rest, I'll follow StackOverflow - I don't have an instant answer, and
the instant answers I _had_ didn't survive second thoughts ;-)
--
Mark Dickinson added the comment:
Just for fun, I posted a Stack Overflow question:
https://stackoverflow.com/q/62721186/270986
Let's close this here.
--
resolution: -> not a bug
stage: -> resolved
status: open -> closed
___
Python tracker
Mark Dickinson added the comment:
One note: in the original post, not only are the values being tested coming
from NumPy's arange, but round(x[i],1) is testing *NumPy's* rounding
functionality, not Python's. x[i] has type np.float64, and while np.float64
does inherit from Python's float, it
Tim Peters added the comment:
Cool! So the only thing surprising to me here is just how far off balance the
arange() run was. So I'd like to keep this open long enough for Mark to
notice, just in case it's pointing to something fishy in numpy.
--
Steven D'Aprano added the comment:
If you change the starting point of the rounding away from zero, the bias flips
back and forth, which is exactly what I would expect from Banker's Rounding:
def check_bias(start):
d = 0.001
ne = no = 0
for i in range(1000):
Tim Peters added the comment:
I assumed Mark would tell us what's up with the arange() oddity, so let's see
whether he does. There is no truly good way to generate "evenly spaced" binary
floats using a non-representable conceptual decimal delta. The dumbass ;-) way
doesn't show a
Steven D'Aprano added the comment:
Thank you for your long and detailed bug report, but please post one issue per
bug report.
Tim, we agree that the notion of significant figures is irrelevant; is Carlos'
even/odd test sufficiently flawed that we should close this bug report, or keep
it
Carlos Neves added the comment:
Hi Peters,
I will pay more attention to the Python docs :)
Thank you for your direction.
Carlos A. Neves
Em qui., 2 de jul. de 2020 às 18:22, Tim Peters
escreveu:
>
>
> Tim Peters added the comment:
>
> For the first, your hardware's binary floating-point
Tim Peters added the comment:
For the first, your hardware's binary floating-point has no concept of
significant trailing zeroes. If you need such a thing, use Python's `decimal`
module instead, which does support a "significant trailing zero" concept. You
would need an entirely new data
New submission from Carlos Neves :
Hi,
I am observing unexpected behavior with round built-in function about (1)
significant figures in analytical methods and (2) number of odd and even
numbers obtained by this function.
https://docs.python.org/3/library/functions.html#round
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