Theoretically you have to use lock, while accesing the isgood instance, but... practically noting bad can happen IN THIS PARTICULAR CASE, if you don't. Python uses Global Interpreter Lock. In other words only one thread is running at any particular moment. Thread scheduling is preemptive, but "atomic" actions are not interrupted. Bollean asigment is an atomic action.
WELCOME TO THE POWER OF MULTITHREADING :) -- http://mail.python.org/mailman/listinfo/python-list
