Why 3.0/5.0 = 0.59999...

[Davy]

Hi all,

I used to be a Matlab user. And want to use Python to replace some
Matlab work.

When I type 3.0/5.0, the result is 0.59999...

Is there some precision loss? And how to overcome it?

Any suggestions will be appreciated!
Best regards,
Davy

[Dale Strickland-Clark]

Re: Why 3.0/5.0 = 0.59999...

Have you looked at the decimal module?

python
Python 2.4 (#1, Mar 22 2005, 21:42:42)
[GCC 3.3.5 20050117 (prerelease) (SUSE Linux)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.[color=blue][color=green][color=darkred]
>>> from decimal import *
>>> Decimal("3")/Decimal("5")[/color][/color][/color]
Decimal("0.6")[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

I don't suppose it is quick but it might do what you want.

Davy wrote:
[color=blue]
> Hi all,
>
> I used to be a Matlab user. And want to use Python to replace some
> Matlab work.
>
> When I type 3.0/5.0, the result is 0.59999...
>
> Is there some precision loss? And how to overcome it?
>
> Any suggestions will be appreciated!
> Best regards,
> Davy[/color]

--
Dale Strickland-Clark
Riverhall Systems - www.riverhall.co.uk

[Mirco Wahab]

Re: Why 3.0/5.0 = 0.59999...

Hi Davy
[color=blue]
> When I type 3.0/5.0, the result is 0.59999...[/color]

try:
[color=blue][color=green][color=darkred]
>>> print (3.0/5.0)[/color][/color][/color]
0.6
[color=blue]
> Is there some precision loss? And how to overcome it?[/color]

Make sure the result gets piped
through some floating point con-
version (like print, %s etc.)

BTW, the 0.5999999999999 9998 value
is the "exact" calculated value
corresponding to your floating point
accuracy (34/2 digits).


Regards

Mirco

[Jeremy Sanders]

Re: Why 3.0/5.0 = 0.59999...

Davy wrote:
[color=blue]
> Is there some precision loss? And how to overcome it?[/color]


See

http://docs.python.org/tut/node16.html

for some useful information.

--
Jeremy Sanders

http://www.jeremysanders.net/

[Grant Edwards]

Re: Why 3.0/5.0 = 0.59999...

On 2006-05-09, Davy <zhushenli@gmai l.com> wrote:
[color=blue]
> When I type 3.0/5.0, the result is 0.59999...
>
> Is there some precision loss? And how to overcome it?[/color]

Doesn't anybody read the FAQ? Or even browse through current
threads before posting?

Sheesh. This has been in the FAQ forever, and was answered
again in the group just yesterday.
[color=blue]
> Any suggestions will be appreciated![/color]

I doubt it.

--
Grant Edwards grante Yow! I'LL get it!! It's
at probably a FEW of my
visi.com ITALIAN GIRL-FRIENDS!!