Can you talk a bit about what you're fuzzing for in Python programs? I feel like I have a good understanding of what cluster fuzzing is accomplishing for C/C++ libraries, but less clarity about the goals for managed languages.
Other use cases include using fuzzing to compare implementations of libs that require the same functionality, detecting invariant violations, testing implementations that are meant to work together (i.e. serialize(deserialize(x)) == x).
In general fuzzing C/C++ libraries for memory bugs is the most commonly described use-case, but I think there are tons of fuzzing use cases that haven't been thoroughly explored yet.