Portably generating infinity and NaN

[Michael Hoffman]

What's the best way to portably generate binary floating point infinity 
and NaNs? I only know two solutions:

1. Using the fpconst module proposed in IEEE 754, which I believe shifts 
bits around.

2. Using an extension module (for example, numarray.ieeespecial will do it).

I thought of using float(Decimal("nan")), but apparently 
Decimal.__float__(self) is float(str(self)), which isn't portable.
-- 
Michael Hoffman