The decimal-c branch is an attempt to rewrite the decimal module in C _decimal builds as a regular stand-alone python extension module decimal.py and test_decimal.py are copies from the 2.5 trunk At the beginning decimal was meant to inherit from _decimal, and wrap not implemented functions. Now, when almost all functions work properly it is not necessary. Edit the Makefile to point PYTHON_25 to point to a trunk build of python and then run 'make' or 'make all' to build the extension and run the test suite.