+/-infinity in Python?

[Andreas Neudecker]

Hi.

Is there anything like +infinity and -infinity available in Python, and
can it be used in comparisons together with int or float numbers?

Regards


Andreas

[Peter Otten]

Re: +/-infinity in Python?

Andreas Neudecker wrote:
[color=blue]
> Is there anything like +infinity and -infinity available in Python, and
> can it be used in comparisons together with int or float numbers?[/color]

To lazy to look it up, so let's try:
[color=blue][color=green][color=darkred]
>>> oo = float("infinity ")
>>> noo = float("-infinity")
>>> oo/noo[/color][/color][/color]
nan[color=blue][color=green][color=darkred]
>>> oo/2[/color][/color][/color]
inf[color=blue][color=green][color=darkred]
>>> noo/2[/color][/color][/color]
-inf[color=blue][color=green][color=darkred]
>>> 10e10 > oo[/color][/color][/color]
False[color=blue][color=green][color=darkred]
>>> 10e10 < oo[/color][/color][/color]
True[color=blue][color=green][color=darkred]
>>>[/color][/color][/color]

:-)

Peter

[Magnus Lie Hetland]

Re: +/-infinity in Python?

In article <bp5tl4$r2t$03$ 1@news.t-online.com>, Peter Otten wrote:[color=blue]
>Andreas Neudecker wrote:
>[color=green]
>> Is there anything like +infinity and -infinity available in Python, and
>> can it be used in comparisons together with int or float numbers?[/color]
>
>To lazy to look it up, so let's try:[/color]
[snip]

Looking it up might be good, though... See, for example, PEP 754,
"IEEE 754 Floating Point Special Values":

http://www.python.org/peps/pep-0754.html

The problem is that the expression float('infinity ') works on some
platforms, along with float('Inf'), but, as the PEP points out, on
many systems you'll just get an error. You could also try stuff like
float(1e3000).

So, my response to the original question would be "sort of" -- since
it's there, but it's not particularly reliable. Let's just hope that
PEP 754 (or something similar) is accepted; infinity _is_ certainly
useful...

--
Magnus Lie Hetland "In this house we obey the laws of
http://hetland.org thermodynamics! " Homer Simpson

[Alexander Schmolck]

Re: +/-infinity in Python?

Andreas Neudecker <a.neudecker@un i-bonn.de> writes:
[color=blue]
> Hi.
>
> Is there anything like +infinity and -infinity available in Python, and can it
> be used in comparisons together with int or float numbers?[/color]

The newest version of numarray and scipy should offer the functionality you
want (at least for supported platforms).

'as

[Andreas Neudecker]

Re: +/-infinity in Python?

Hello Peter, Magnus,

thanks for your hints.

I will read the PEPs first, because I need compatibility at least for
Linux and Windows ...

Kind regards


Andreas


Andreas Neudecker wrote:[color=blue]
> Hi.
>
> Is there anything like +infinity and -infinity available in Python, and
> can it be used in comparisons together with int or float numbers?
>
> Regards
>
>
> Andreas
>
>[/color]