[CentralOH] Arithmetic With Units

[jep200404 at columbus.rr.com]

What Python packages handle arithmetic with units? 
In other words, what package would do something like below: 

>>> d = Foo(176.0, 'feet')
>>> t = Foo(2.0, 's')
>>> speed = d / t
>>> print speed
88.0 feet/s
>>> a = 2.0 * d / (t ** 2)
>>> print a
88.0 feet/s^2