Setting longer default decimal precision
Kay Y. Jheallee
nospam at use.net
Wed Nov 20 20:34:55 CET 2013
On 13.Nov.20.Wed 14:02, Steven D'Aprano wrote:> Hi Kay,
> You emailed me off-list, but your email address is bouncing or
> so I have no way to email you back.
So THAT's where it went! Sorry about that...yes, it WAS meant
for the group :/!
> [you wrote]
> Okay,but after I import "math" and "decimal",
> py> decimal.getcontext().prec=75
> py> print decimal.Decimal(math.atan(1))
> though I set precision to 75, it only did the trig function to
> 50 places AND it is only right to 16 places,
> [end quote]
> Here, you calculate the atan of 1 using floating point maths,
> that is, to the precision of C doubles (about 17 decimal
> places). After the calculation is performed using float, you
> then convert it to a Decimal,
> but it is too late, you can't retroactively regain precision.
> In a perfect world, this would work:
> but alas, all the functions in the math module convert their
> arguments to float first, so even though your Decimal(1)
> could perform calculations to 75 decimal places, the
> math.atan function downgrades it to a regular float.
Then that is useless! :(
> You could try this third-party module:
Ah, that looks like just the puppy I'm looking for. :)
Okay then, I just installed the PortableApps version of Python,
but when I downloaded "mpmath-0.17.win32" the installer aborted
with "No Python installation found in the registry".
So I'm trying to install "setuptools 1.4" (and do it that way) at
but where is the "Download" link ("Downloads" just shifts down to
the page section)? I'm just looking for the ".zip" file version
(if one exists), not ".tar.gz".
Kill Hector dead, because Desi sent Milli.
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