graphical or flow charting design aid for python class development?

[tooper]

You may want to use Doxygen, which generates nice diagrams. It's
normally only for C++, but there are nice filters (for ex.
http://i31www.ira.uka.de/~baas/pydoxy) that generates C++ header from
python code that Doxygen can crunch.

Another solution is to use IDE such as Eric3 that can generate UML
diags from source code on the fly.