Strange behaviour of floating point constants in imported modules

[Tomasz Lisowski]

Hi,

We are distributing our Python application as the short main script (.py 
file) and a set of modules compiled to the .pyc files. So far, we have 
always treated .pyc files as portable between platforms, but recently we 
have discovered an annoying problem. In a module, there is the following 
code fragment:

Deg2Rad = math.pi/180.0
angleEPS = 0.5
angle0B = angleEPS*Deg2Rad

which calculates 'angle0B' as the angle of a half of a degree, converted 
to radians. The module has been compiled on an English Windows XP 
machine, and then tested on a Polish Windows XP workstation.

What was our astonishment, when various exceptions started to be raised 
on a test machine (no problem on the original English-version Windows 
XP). We have traced them to the fact, that both angleEPS and angle0B 
were found to be ZERO (!!!), whereas in reality, angle0B is about 0.008. 
And this all happened silently, without any error during the import of 
the module!

What's the reason of this error? I start thinking, that it may be 
related to the fact, that the decimal point on the Enlish Windows XP is 
the '.' character, and on the Polish one - ','.

Is there a good method to avoid this kind of problems? How to make such 
distributed modules really portable?

Thanks in advance
-- 
Tomasz Lisowski