Python (the language) makes no guarantee itself on what the precise
semantics of floating-point operations is. This is documented in

http://docs.python.org/ref/types.html

"These represent machine-level double precision floating point numbers.
You are at the mercy of the underlying machine architecture (and C or
Java implementation) for the accepted range and handling of overflow."

If you want to, one could add ", precision" in the sentence; I think it
is fine as it stands.