Decimal vs Float comparasion

[Yuan HOng]

Hi,

It seems decimal object will always be larger than float in
comparasion, which goes against common sense:

>>from decimal import Decimal
>>a = Decimal('0.5')
>>a 99999

False

>>a 99999.0

True

It seems to me that rather than allowing this to happen, comparasion
between the two should either be made correct (by convertion decimal
to float e.g.) or forbidden, like arithmatic operations between the
two types.

--
Hong Yuan

´ó¹Ü¼ÒÍøÉϽ¨²Ä³ ¬ÊÐ
×°ÐÞ×°ä꽨²ÄÒ»Õ ¾Ê½¹ºÎï

http://www.homemaster.cn

[Gasto]

Re: Decimal vs Float comparasion

I still don't see why such a module exists.

On 5 mayo, 21:52, "Yuan HOng" <hongyuan1...@g mail.comwrote:

Hi,
>
It seems decimal object will always be larger than float in
comparasion, which goes against common sense:
>

>from decimal import Decimal
>a = Decimal('0.5')
>a 99999

False

>a 99999.0

>
True
>
It seems to me that rather than allowing this to happen, comparasion
between the two should either be made correct (by convertion decimal
to float e.g.) or forbidden, like arithmatic operations between the
two types.
>
--
Hong Yuan
>
´ó¹Ü¼ÒÍøÉϽ¨²Ä³ ¬ÊÐ
×°ÐÞ×°ä꽨²ÄÒ»Õ ¾Ê½¹ºÎïhttp://www.homemaster.cn

[Marco Mariani]

Re: Decimal vs Float comparasion

Gasto wrote:

I still don't see why such a module exists.

There are 2.0 types of programmers: those who always use floating point,
and those who know how to use them.

[Erik Max Francis]

Re: Decimal vs Float comparasion

Dennis Lee Bieber wrote:

On Tue, 6 May 2008 11:52:10 +0800, "Yuan HOng" <hongyuan1306@g mail.com>
declaimed the following in comp.lang.pytho n:
>

>It seems to me that rather than allowing this to happen, comparasion
>between the two should either be made correct (by convertion decimal
>to float e.g.) or forbidden, like arithmatic operations between the
>two types.

>
Why should decimal be coerced to float? Maybe float should be
coerced to decimal?
>
Or... the programmer should explicitly specify what comparison is
wanted -- if any...
>
Or... Isn't Python 3.x supposed to forbid mixed type comparisons
unless the types implement suitable handling?

Bottom line is that it shouldn't silently return something insane.
99999.0 is surely exactly representable in any modern floating point
system, being a floating point representing of an integer, so silently
returning a completely invalid comparison is a tremendously bad idea.

It's a bug.

--
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis
Can I walk with you / 'Till the day that the world stops turning
-- India Arie

[Rhamphoryncus]

Re: Decimal vs Float comparasion

On May 6, 1:31 am, Dennis Lee Bieber <wlfr...@ix.net com.comwrote:

On Tue, 6 May 2008 11:52:10 +0800, "Yuan HOng" <hongyuan1...@g mail.com>
declaimed the following in comp.lang.pytho n:
>
>
>

It seems to me that rather than allowing this to happen, comparasion
between the two should either be made correct (by convertion decimal
to float e.g.) or forbidden, like arithmatic operations between the
two types.

>
Why should decimal be coerced to float? Maybe float should be
coerced to decimal?
>
Or... the programmer should explicitly specify what comparison is
wanted -- if any...
>
Or... Isn't Python 3.x supposed to forbid mixed type comparisons
unless the types implement suitable handling?

Yes, it is fixed in 3.0. Unfortunately it's well established
behaviour in 2.x, so it won't be changing there. Don't bother
reporting a bug about this unless it's about 3.0.