Replaced the call to execfile (does not exist in Py3k) with runpy (introduced in Python 2.5). Also made some stylistic changes so that the file conforms to PEP8.
I'm happy with updating the code to make it Py3k compliant. However, note that I have never tried to compile PyMaxflow in Py3k and there might be both compile time and runtime errors.
Replaced the call to execfile (does not exist in Py3k) with runpy (introduced in Python 2.5). Also made some stylistic changes so that the file conforms to PEP8.