I have Python 3.1 and the PythonCard installer recognized it, but it was going crazy about installing PythonCard for Python 3.1 because the installer consisted of Python 2.x, and when I tried to run PythonCard, I got a SyntaxError in C:\Python31\Lib\site-packages\PythonCard\model.py, and I had to 2to3 it, but the lib2to3 was corrupted, so I had to use my brain to find the changes from Python 2 code to Python 3 code. Now, I will give you the Python 3 version of model.py
Python 3 version of PythonCard's model.py