Python's float type is double precision.
Look at the position where the numbers are rounded. 


Result on Python 2.0 (or 2.1 alpha 2)

>>> 0.8
0.80000000000000004
>>> print 0.80000000000000004
0.8
>>> print 0.8000000000004
0.8
>>> print 0.7999999999999
0.8
>>> print 0.7999999999995
0.8
>>> print 0.7999999999994
0.799999999999



Result on Jython 2.0

>>> 0.8
0.8
>>> print 0.80000000000000004
0.8
>>> print 0.8000000000004
0.8000000000004
>>> print 0.7999999999999
0.7999999999999
>>> print 0.7999999999995
0.7999999999995
>>> print 0.7999999999994
0.7999999999994

Logged In: YES 
user_id=21627

What is the bug that you want to report? It is perfectly
fine that CPython and Jython behave differently in this
respect. CPython uses the C double type, and inherits all
its semantics; Jython uses the Java double type - which
might be different, since the C standard does not say what
double is (only that it is more precise than float).

If you meant to report a more specific problem than the mere
difference, please re-report.