My previous announcement on this was only nine days ago, but in retrospect I think that release was premature. I have made substantial simplifications and improvements since then. Here is the abstract from the three-page user guide (which is in PDF):

A Python class was designed to represent physical scalars and to eliminate errors involving implied physical units (e.g., confusing angular degrees and radians). The standard arithmetic operators are overloaded to provide syntax identical to that for built-in numerical types. The scalar class allows the user to easily define a set of appropriate physical units for any particular application or domain. Once an application has been developed and tested, the units can easily be switched off, if desired, to achieve the execution efficiency of operations on built-in numerical types (which can be two orders of magnitude faster). The scalar class can also be used for discrete units to enforce type checking of integer counts, thereby enhancing the built-in dynamic type checking of Python.

Give it a try. If you do scientific or engineering computation, I bet you'll like it!

http://RussP.org/scalar.htm