Maybe I'm missing something, but if you can set os.urandom to a custom function, why not implement your own stateful PRNG in python and patch urandom to point t

Maybe I'm missing something, but if you can set os.urandom to a custom function, why not implement your own stateful PRNG in python and patch urandom to point to that? Then you can, among other things, seed the PRNG yourself in unit tests, all from within python and without touching syscalls.